Almost every kart brand has a “seat chart” with recommended placement depending on the driver size and chassis model.
There is some leeway where you can place the seat within the fixed seat posts. You might need to bend them or fill space with seat spacers.
The general rule is to measure from the rear axle to the back of the seat.
Single gear big chassis roughly 15cm
KZ 11-12cm
I don’t like the manufacturers charts because that is based on a certain size of seat. Every seat has different shapes depending on size so the back is a lot more accurate to measure from
Bored and reading a TKart article on the 401 RR, saw this and this thread came to mind. OTK makes cassettes with a 5mm offset!? If this is true how do I get a set to try?
Maybe I just answered my own question… By misaligned does that mean the bore for the bearing is offset 5mm or 10mm?
Yep, you have different cassettes for different offsets. Really awkward stuff and very time consuming to do😆 You will also need 2 extra bearings etc for “faster” changes.
KR and Crg has this built in where you just rotate cassette forward or rearward to get different wheelbases.
Seems like that KR/CRG method also changes rear ride height?
Pretty much all modern karts allow for ride height change with multiple holes drilled in the bearing hangers. What’s nice about the KR/CRG is the ability to just flip the cassettes around to change wheelbase. OTK looks like I’d need a whole new set of cassettes and bearings, so about $300 minimum just to try a setup change. About $500 if you run the 3rd bearing 
We’re building chassis this year with independent wheelbase and ride height adjustments.
I don’t think the cassettes have to be flipped. They are rotated, but the various holes & their geometric offsets can maintain or adjust the height as desired. Pretty nice. Others should follow suit. Same for their innovative VEN13 “antilock” brakes.
Got to test the two prototypes of the mini chassis almost exactly a month after I posted that. Felt much better. I’m pretty sure that’s in manufacturing now. The first one was the worst thing I’ve ever driven, the second one was golden.
