3 across in Volvo XC90

My friend is expecting twins (they already have a 2yr old) and they have an XC90. I gave them my MA65 which we have in the middle and they have an Onboard 35 infant seat. We were testing to see if the infant seat will fit on the side (before ordering a 2nd one). There is room (just barely)...however, because of the contour of the seatback, both sides curve around (like a bucket seat) and because of the contour base where it meets the seatback, when I tested side-to-side I got a lot more than 1". I tried both LATCH and seatbelt and both were extremely taut and still allowed too much movement. I should have taken a picture or video!

I'm wondering if the deluxe base for the Onboard Air would solve the issue because it would be "locking" the seatbelt in the middle (started to get tilt at the retractor side). The seat also put both parents a little farther forward than desired, but it would be the cheapest option if it works at $170: deluxe base ($70) plus new car seat that comes with deluxe base ($100)

I don't think they want to spend a ton of money since they will have a lot of expenses coming up. The pregnancy is very high risk (Mo-Mo twins--the rarest kind) and mom will be in the hospital starting at 26 weeks until delivery (hoping for 32-36wks) and babies will be spending time in the NICU, etc.

I looked on carseatblog for the recommended preemie seats, are there others that might fit the contour of the seatback, but not be so long front-back? The Evenflo Embrace was the other budget option, beyond that, I'm thinking Snugride 35 is the next cheapest option. Albebaby has one with the 4lb minimum for $114. She only has 3 weeks or so before she goes into the hospital so she wants to get things nailed down soon.

Any ideas and recommendations would be great! I've been a tech for 11 years and there are still surprises and head-scratching situations!

Check these out and see if they would puzzle w/the MR:

http://www.kmart.com/cosco-comfy-ca...W029360270001P?prdNo=5&blockNo=5&blockType=G5

They are actually a pretty nice seat. Not a lot of padding, but they go from 4-22 lbs. They are super lightweight, the lowest harness slot IS low enough for a preemie. (I had 2 preemies, one born at 29wks/2.5 lbs, the other at 35wks/6 lbs.)