I wear a GQ 350 parachute in our RV-8 for some flight profiles (mainly displays/practices) - mainly "seat back" type, but some of the chute is "seat". I tried a few, and most pushed my back too far forward, especially low down. I leave the bottom cushion(s) in place, and remove the (front seat) rear cushion.
"I modified a stock seat back with a bend in it to make the seating posture more comfortable." Ditto without being aware of what Steve did
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Is better... however, it does require the rear stick removed to full forward deflection. So swap seat backs for 2 up flying.
There are some "rules" re parachutes drilled into me over a flying career (or by others who have much more experience):
Parachutes can be ruined in a short time by being stored incorrectly. Apart from the very occasional overnight stay, that means removal from aircraft and storage in a suitable environment after flight.
You should, post flight, unstrap from the aircraft and exit with the parachute on - if you routinely disconnect the parachute then you will do the same reflex action under severe stress should you need to "jump". If the chute is being used again a few hours, climb out with it, take it off, put it in aircraft.
I have enough doubts you could abandon an RV-8 from the front seat. I have severe doubts you could from the rear seat, especially if the front seater has "gone".
Also agree with Paul's comments on straps.
Through unfortunate / tragic events, much of the above has been learned. Also, little point in wearing a parachute if you do not wear a helmet. The helmet is more likely to be needed in typical accidents, and keep you conscious enough to deploy the chute as you jump out and bang the tail etc.
Link (
http://www.mod.uk/NR/rdonlyres/7EFF...AC1F/0/maas85_03_bulldog_t1_xx660_25mar85.pdf ) - successful "jump" but undid parachute harness as well (reflex action) = fatal. This accident resulted in after every flight you climbed out with the chute on, removed it alongside the aircraft.
Link (
http://www.guardian.co.uk/lifeandstyle/2011/aug/12/i-crashed-vintage-plane/print ) - successful low level abandonment (<1000' mid-air)
"There was a deep gouge in my flying helmet – evidently, my head had bounced off the tail as well does not sound like he would have been in a good position to deploy the chute if he had not been wearing a helmet?"
From a recent (fatal x 2) accident, it has been highlighted (yet again) that owning and wearing a chute is but a small part of the "solution". You must have clear ideas/rules about when you will use it, the procedures (and calls / liaison if 2 occupants) to get out, the minimum heights for commencing abandonment - derived from that specific chutes "min deployment height". And such egress drills rehearsed regularly (monthly?)...