The best foam to use for pews & kneelers is our very firm reconstituted foam. The depth we recommend for pew seating is 2” deep but any depth as thin as 0.5” can be cut. For kneelers the most popular depths we receive requests for, are 3” and 4”. The durability of our reconstituted foam means that you will get many years of use out of the cushions.
For Church seats, we can cut foam to shape. Again we can use our reconstituted foam but we tend to find that our high/firm grade is the most popular as it is easier to work with when the foam needs to be compressed at the edges of the seat.
Both David & Sally at foamcushion.co.uk are active in their local Churches and hence can advise you from a position of experience.