the 5th point dilemma...
Glenn,
I'm trying to do exactly the same thing, so here's what I've found so far.
My belts say 'amsafe' on them, pretty sure that was what Van's supplied in 2005 or so. Their site clearly says something like ' 5 point will NOT work with 4 point harness'.
I tried simply attaching on of the passenger shoulder attach tabs to my 4-point, and, well, it works, but there is really no slack left on the lap spade. In fact, about 50% of the time, I couldn't latch it without juggling all the connectors. So it will work, but not reliably in my opinion.
I contacted one of the suppliers that makes the 5th point connection , and they said they were not in stock, but could make me a batch .
P/n RH-54s
These are a special order and are made for the Am-Safe style seat belt buckles and connectors. $20.00 each, 10-14 days. Minimum is 25 pieces. [email protected]
Maybe we should talk to Allan Nimmo at AntiSplat eh?
I'm seriously considering making all cloth loops that attach to the lap belt on each side of the main buckle, kind of like the fancy 6 point 'y' racing belts, and thus do away with the mechanical buckle issue, plus it might be more comfortable if I can get all the geometry correct. ( ie. it will allow a little more 'breathing' room right behind the stick, since that's practically in your lap when full 'up' elevator applied)