I had a few people ask me where I geared my 17.5 in my buggy. I started at 34/72 and the car was a rocket... had a bad spur gear and no 72's available so I went to 75 spur. 34/75 was good too.
I ended up in bad reshuffle and was in with some cars that were significantly slower. The constant braking to avoid peeling someone made it hard to keep my momentum. By dropping down to 33/75, I was able to rip through the infield and clear the jumps while slowing my car down a little bit.
TLDR version
D3.5 20deg timing. Blinky Class
B4.1 2.6 internal gear ratio.
34 / 72 5.505 FDR was best if you could keep a great line and not be tied up in traffic
34 / 75 5.735 FDR was very good and just a little bit slower top end.
33 / 75 5.909 FDR was overall fastest due to traffic.