Bob, you can raise the front of the seat a little by removing the seat base and loosening the front seat bracket quick release. I put a hard rubber washer under the front edge of the bracket which raised it about 1/4". That was enough to prevent sliding forward. If you need more lift, you can put wedges between the seat bracket and the plywood bottom of the seat base.

You will notice that the seat base mounting screws are in slots, so there is some forward/back adjustment of the base in relation to the seat back. Also, by keeping the seat back cover strap at lumbar height fairly tight, you actually get comfortable lumbar support.

I found the best way to fine tune the seat position in relation to the pedals was to get it as far back as possible but still be able to push off the seat back when climbing hills. This takes a few readjustments, but once you get it right on, it really is comfortable. Having this right also reduces sliding forward.

They really are wonderful seats. Happy riding. bk