Question Three Across in Mazda CX-9 (preferably with KeyFit 30)

Hello. I'm struggling to find a good 3 across solution in the second row of my Mazda CX-9.

In March I will have a tall almost 5-year-old son (he is currently 39 lbs and 43"), a very average sized almost 2-year-old daughter and a newborn. Currently my son is in a Chicco NextFit (ff), my daughter is in a Graco Size4Me 65 (rf) and I have a KeyFit 30 that I would very much like to use for the newborn.

My son needs to occupy the middle position with the two youngest children in the outboard spots because I am too small to lift a child over another seat and into the middle spot. I JUST switched my daughter from the KeyFit to the Graco Size4Me and can still return the Graco seat if another model is preferable.

So far, I have unsuccessfully tried the following combos:
NextFit (rf), NextFit (ff), KeyFit (rf)
Size4Me (rf), NextFit (ff), KeyFit (rf)
Size4Me (rf), Size4Me (ff), KeyFit (rf)
Size4Me (rf), Graco Slimfit (ff), KeyFit (rf)

I have tried this with LATCH and I've tried it with seatbelt-only installations. We have tried the KeyFit with and without the base, but don't feel like it installs as securely without the base. One problem we've encountered is that the 2nd row bench seat is not completely flat so even when using the seatbelt instead of LATCH, the seats in the outboard positions cannot sit all the way at the edge of the bench, if that makes sense.

I have seen some posts on this forum that say the Radian fits well next to a KeyFit in this car. I'll probably bite the bullet and buy a Radian next, but would welcome any other suggestions. I honestly am having trouble seeing how the KeyFit can fit in the outboard position next to anything else, but some people seem to have made it work.

Also, for those who have successfully fit a KeyFit on one side of a CX-9 with another seat next to it, did you use the KeyFit base or only the seat? Did you use LATCH or seatbelt only?

Any other tips? Does the order in which I install the seats matter at all?

Any tips or suggestions are welcome.

I don't have much specific advice, but I do know you can't buy a Radian right now. The Diono convertibles are under recall, so none are available right now. Sorry!

My best just bought this car and has a Keyfit 30 (with base) behind the passenger, usually me in the middle and a Graco Tranzitions behind the driver. I have enough room in the middle to sit comfortably. I would probably return the new Graco seat, put the almost 2 year old in the Nextfit, and buy a Cosco finale for the 5 year old.