The idea of the domed pads (apart from grip and padding for impact) was to increase the doming (underfoot curvature) in the standing area on an otherwise "thin" deck profile board. Depending on a bunch of things, this can give the rider more drive through the foot, which can be especially important at high speed and maybe even moreso across chop.
In my experience the pad works better when your foot is well in, over the thicker section (not just sliding back off the back edge of the "ramp"). Best set up to achieve this depends a little on the riders foot size/shape (obviously larger feet reaching further fwd in some cases).
If you're using INBOARD (front) settings then the thicker underfoot section is usually in the right spot but requires use of more open straps than normal (just to get your foot in).
When using OUTBOARD (front) settings it's not so obvious - but possibly even more critical to size the straps a little bigger than normal on conventional flat deck/flat pads. This can be more difficult when the straps are brand new (stiff and not broken in).
Also the antitwist K9 has an influence in that if you use them (some riders prefer not..) it adds to the "stack height" under the strap (effectively increasing the room under/inside the strap) - but at the same time K9 resists the normal "wear-in" twist that curves the strap inboard across the top of the foot with use (this also allowing the foot to position further inboard - and in this case- critically- more OVER the pad, rather than falling off the back of it). After a few good sessions the whole thing seems to settle in.
Sailing iS76 fully lit in chop definitely requires commitment for the best results (but they are pretty good when you do..). Having the front foot securely locked down, and not coming unstuck at inopportune moments is critical. Although conventional wisdom would favor OUTBOARD settings for more extreme conditions, when things get really gnarly and rough, it's likely the INBOARD settings that will give a safer, more controlled "extreme" iS76 ride in rough water for the average weight and average foot length rider.
Cheers ~ Ian