mine has no armrests, it may have at one time but I probably junked them. Sounds like it might work! I'm going to do some measuring and I'll report back with what I find. This leads me to the next question-
I'm running 4 point harnesses on the outside two spots on the bench, and will have the original lap belt in the middle position. My plan is to use only the lap anchors for the 4-points to strap the 2 seats in , and the center lap belt to strap the middle seat in. I will be adding the top anchor points for the car seat top straps.
Any issues with this? I will always take it easy when the kids are riding, but I hope I can make this happen. I don't want to have to tell one of them they won't fit