TRX,
I share your concern about the circulation in the legs. There's a lot to consider here.
Attachment:
Caterham-7-Custom-2006-sm.jpg
Speaking personally, I don't imagine my backside is going to rest solely in the lower area. If it can't settle comfortably on to that lower section, I wonder how the lower back will handle that. The one picture found of a used seat bottom suggest, to me, that there is a good bit of "give" to the bolster.
Attachment:
Caterham-160-06.jpg
Research would indicate there is a wide range of foam densities available. Trail and error my be the best approach for matching the type of material to the individual.
After all, like every other part of our 7s, this is just another chance to do it your way.
As far as cutting off the blood flow, the cars these were designed for have a cockpit that is shorter than most lowcost builds.
For many years the frames were very similar to the original series 2. The result being, the legs don't exactly lay flat.
Where the book frame measures 32" from bulkhead to the first vertical piece, the original is under 24".
Attachment:
Original frame specs,01.jpg
Also the original height at the top of that vert. was 13.25 compared to 15" for the McSORLEY 7+442e frame. So with the side tube angled down toward the rear, the seat sit high enough for the elbow to clear to side while driving.
Most of this long winded explanation is to help me to reorganize my thoughts again, so please don't take offense if I'm stating the obvious or what is common knowledge.
Attachment:
caterham-roadsport-175-1.jpg
Notice the dropped floor pan on this Roadsport.
Attachment:
Caterham-Dropped seat pan05.jpg
Maybe that was added to help with leg comfort.
Ron