One thing to try is get some 1/2" or 3/4" pvc pipe or a wooden dowel...cut it about 6-8" and then tuck it between the seat bottom and seatback...that should tighten them up.
Looking great...trac bar is a definet with soa...Just a fyi that fabric filter stuff you used is HIGHLY flammable you may want to keep an eye on it with all the heat underhood...if you see any spots that look like it melted scrap it.
Just got my invite from Shaggy, decided to pop in and see whats going on...I got a '61 Willys CJ5, a '70 CJ5, and a '71 Jeepster Commando, so anything dealing with the older models I'll try to lend a hand where I can.--Dan.
