I have personally gone through this delema myself and I'm only 5' 11". What I discovered and what seems to be the most important issue is the design of the seat....let me explain. Many of the aftermarket seats have a shell that supports the seat cuchions. This style seat, if mounted to the stock seat mounts (240, 260, 280) will raise you up and inch or more, depending if you install sliders or not. However, seats that have a similar design to stock seats, actual butt cushions that are suspended via straps, allow you to sit lower. A couple of seats you may want to look at are the entry level race seats by either SPARCO or MOMO. They are priced at around $200.00 each and are fixed (do not recline). I have the SPARCO "Sprint" seats in my 240, without any sliders, mouted directly to the stock seat mounting locations and have more than sufficient head room....even with a helmet on. Hope this info helps some!