DC - great install doesn't stay great...help

I am installing a DC RF outboard in an F350 with leather seats. I am not using either lock off because they are a pain. I am just locking the seatbelt (this may be the root of my problem). I am getting a great install with no movement at the belt path. The base is nice and flat on the seat. I pull the seat out from the bight a little so I could get a more upright install (this may also be a problem).

The issue...after a few weeks, the base is not flat on the seat anymore. The install is still very tight but the base gets "jacked" up on one side. Any advice to make my install last longer. I am sure that 80% of the base is still touching the seat but since I know that I can get an install with it all flat on the seat, I feel the need to keep reinstalling it. Anyone?

You have a switchable retractor?

The problem is that you are locking the shoulder belt. With a rear-facing installation, most times, a locked shoulder belt will cause the seat to tip over time (if not immediately).

Do you know if your latchplates lock? Sit in the seat and buckle the seatbelt over you and pull it tight (do not lock the shoulder belt). Now tug on the lap portion. If you can pull it out, your latchplates do not lock and you will need to try to use the RF lockoffs. If you cannot pull the lap portion out, your latchplates do lock and you don't need to do anything except install the seat (don't have to lock shoulder belt or use lockoffs).

I've found, that with the RF lockoffs, it's mostly about the angle. I thought I couldn't get them to work in my car, but much to my surprise, I got one to work just fooling around with it the other day. What you have to do is put both the lap and shoulder portions inside the lockoff furthest from the buckle. The lap portion should go toward one side of the lockoff and the shoulder portion to the other side, so they are just overlapping in the center of the lockoff. Then push the lockoff closed...it might not snap immediately, but keep pushing and also use your knee/weight to put pressure on the foot area (where kiddo's feet go) of the Marathon to change the angle a bit (that's what did the trick in my car).

I know that's not the best explanation, but hopefully it makes some sense!

No that was a very good explanation. We do not have locking latchplates and I figured that locking the shoulder belt was my issue. Darn!! I have used the lockoffs before but I felt I could get a tighter install when locking the belt and not using the lockoffs. I guess I will try again. Thank you so much Sam.

You're welcome! I'd definitely give the lockoffs another try! Install it as tight as you usually do and then just wiggle the seat to get the lockoff closed...hopefully it'll work perfectly!

Your advice was great. It worked perfectly. The seat is rock solid (probably more so than before). I used the lock off opposite the buckle and it worked like a charm. No more tipping. My hate for the lock offs came when I tried to install it in my car. If I ever need to install it back in my car, I think I will just stick with LATCH...ha ha. Thank you very much for making me give the lock offs a second chance.

You're welcome! I'm glad you were able to get them to work!