19lbs at 4.5 months old puts your son in the 90% for weight. IF he stays on the same growth curve, then he would be 30lbs at 17 months and 35lbs at 2.5 years old. With that said, most four month olds do *not* stay at 90% - they start to even out once they are crawling/walking.
If you are planning on rear facing to the limits of the seat and want him rear facing longer (2 - 3 years old), then you may want to go the TruFit option for the 35lbs limit.
I find the Trufit to be slightly annoying with installing because of the *need* to use the lock-offs. I also can't stand the infant padding in the Trufit as I believe it interferes with the harness when tightening/loosening... just makes one more thing for the harness to catch on. These are issues you can work around if you know about them though.
You do need to be *extremely* careful with tightening the harness. The straps are folded over in the buckle tongues which causes the buckle tongues to stay in place (they will not slide down to hide by the hips), however this means the buckle tongues do not slide freely along the harness.
I recently had a check where the mom put her baby in, tightened the harness and checked the tightness using both the pinch test and the one finger method. The harness appeared tight and she had pulled hard to get *all* slack out of the seat. *However*, due to the straps being folded over in the buckle tongues, there was still excess harness by the hips... about an inch or so.
You *need* to buckle the harness and pull all the slack out of the *hip area* before you pull on the strap to get the rest of the slack out of the harness. If you are diligent with this, then you will be fine using this seat. If you are not, it will never be tightened correctly.
The harness is a continuous loop harness. It starts at one shoulder and goes down past the crotch strap to the hip, under the bum, up past the second hip through the crotch strap and up to the second shoulder. Essentially you don't need to loosen/tighten the harness every time because you can just tug by the hips and slide the strap back/forth to have it loose on each side as you put that arm through the strap.
This works great when rear facing. However once forward facing, I've found that the way the child sits in the seat (or maybe the heavier weight of the child - mine was 39lbs) does not allow the harness to slide back/forth easily at all.
I also *really* do not like this seat in forward facing mode, it is quite reclined and I'm just not okay with a forward facing seat being that reclined.
If you are okay with turning your child forward facing at 17 mo, or want to take the gamble that they will slow down in weight gain (most children do, but not all) then you have a few other options.
Britax Marathon
-older children do find it narrow through the shoulders
-I love the rear facing tether and I really like how it fits kids when rear facing... if you are planning on having another child down the road, you can plan to pass this seat down to the new baby once your son goes forward facing/outgrows the seat... then purchase a seat like the Frontier/Nautilus/whatever is latest and greatest on the market for your son.
Sunshine Kids Radian
-tallest top slots of all convertible seats on the market (
comparison photo thread here)
-rear facing tether
-*fantastic* for airline travel once forward facing (after a year on the plane - rear face at your destination until the limits of the seat)
-can be tricky to install the first few times... once you
learn the tricks, it's fairly simple
-takes up quite a bit of space when rear facing... so knowing your vehicle make/model/year helps quite a bit in choosing a seat
-very narrow outside footprint which makes three across much easier and allows larger adults to sit in back beside the seat comfortably
Evenflo Triumph Advance
-small front to back space
-has knobs for adjusting on the side of the seat which can sometimes interfere with the vehicle seat when rear facing... if you have sculpted back seats, this is probably not the seat for you
Your last option and probably the one I would choose is to get a SafeSeat1 like a previous poster mentioned.
A carrier will still allow you to take baby in/out of the vehicle without disturbing sleep for those quick in/out trips at the gas station/grocery store/mailbox... you know, the errand days where it's just not worth disturbing their sleep.
For the other days, just leave the carrier in the vehicle and take baby out with you.
It will also be super nice with our winter coming to not worry about how your going to safely bundle baby, get them to the vehicle, put them in their seat and then cover them with blankets. Remember that kids should *NOT* be wearing bulky snowsuits in the vehicle. They allow slack in the harness and then baby is not tightened correctly and runs the risk of being ejected in a collision.
With a carrier, you put them in and buckle, add blankets around them and then if you want you can add a pop over cover to keep them warm on the trip to the vehicle.
I had to take both my kids out of the carrier at 5 months (too tall and no SS1 option at that time) and I *hated* not having the carrier any longer... especially since they both came out of the carrier in September (Saskatchewan) and October (Alberta)... not fun winters.
The SS1 should last your son until close to 17months as well, that this is the option I would go and then see what great convertibles are out at that time.