I use one with a large flat seat slightly inclined towards the front. Actually, it was my office chair until the armrests broke. They held the back part as well, so just the seating pad was left, and I use it now turned back to front. This promotes also an upright posture. I replaced the gas spring with a longer one. I need a seat height of 60-65cm due to long lower legs and worn knees. Such a seat is hard to come by. I encountered the “numb crotch” problem with severeal mushroom shapeds seats, if the need for replacement arrives one day, I’ll ask a professional to fabricate an upholstery to my measure.
Hi Ronald,
Years ago I followed the advice that Scott Pilkington gave in one of his instructional videos. That is; make sure that your feet are flat on the ground, your knees are more-or-less parallel to the floor, and your back is straight.
A Chiropractor friend of mine says that it's good advice for engravers.
Here is a photo of an old office chair that was surplus from a U.S. Govt. installation. It sold at auction for $40.00. It's my favorite and very comfortable. Hope this helps.
B