We are looking at getting a convertible (2SS or LZ1 still undetermined) but we have 2 kids, ages 3 and 1. I am 6'5", 200lbs, wife is 5'3 115lbs.
What I found is as long as I put the front facing seat behind the driver, it is doable. No it isn't the most comfortable but I can sit in either seat semi comfortably. In front of the rear facing seat is worse, hence why it's behind the passenger seat. I will be sitting in both drive and passenger seats.
I was also able to squeeze into the rear seat behind the driver (still in same position where I could drive) very uncomfortably but for a short ride, possible. Thankfully this will never happen.
My head grazes the roof liner in this configuration in both the driver and passenger seats.
All pictures are with the seats in the same spot.
