Greg
No, I did not form any holes, but it was suggested at Rawles that I did.
On the passenger side there is no seat adjuster on my car so I just put the foam in as received, having checked the head room to the top first.
On the drivers side there is a seat adjuster so that raises the base up, I ended up cutting 1.25 inches off the base of the foam - still no holes.
I found the seats comfortable built this way, some may think that they are a bit stiff and you do not sink into them much but I like it that way. I have no need to have the cushion grip the rear end like a bucket.
Having said that, I took both seats apart again after the first fitting of the covers. In the first one I found that I needed to pad out the central section as the covers appear to be 'home made' by a PO and did not include padding in the ribs, it looked really bad without some central padding. On the second one I included padding first time around but it was the head room issue, I trialed it without cutting and determined that I needed to cut something off in the region of 1" to 1.5", not wanting to screw it up I took a 5/8" slice off, stuck it all together - clips and glue an rivets and tested it, I had to remove clips and rivets and ease the cover off the bottom of the pan, keeping the cover glued to the top of the foam and trimmed another 5/8" off the foam. I kept the foam from the front gear box side and stuck it back on but outside the pan, as there is a big overhang - pan to foam, on that corner, I felt that it helped keep the line on the finished work. What I am getting around to in a long winded way, is that you can always cut holes in the base of the foam after if you do not like the feel of the seat, without too much effort.
Bob
Dave - I have no info on refurbing the seat backs, I did not intend to do anything with them at this moment and did not ask the upholsterer for any tips, so go with Randy on that one.
Bob