Hey folks! I am selling my 40hp Himax to a gentleman that is 6ft 4in. Is anybody of a similar height able to fit into the Himax? I am 5ft 8in and never had issue, but I am much shorter.

This gentleman is also ~230lbs. This leaves him with ~10-15lbs of fuel. Does anybody operate 10-15lbs over max on 40hp? I know that the gross on an experimental is basically a strongly recommended "suggestion" but it is set for good reason. Is there a significant structural danger to doing so?

I will say that I have been guilty of this 3 times in a C172's and a PA28R where I knew an extra 15lbs (always well within the CG envelope) on a good sized runway was not a huge risk. I am not condoning, nor will I encourage/suggest for him to do so. I am curious because I know the temptation is an easy decision for a new buyer and new pilot.

Any feedback is appreciated.

Regarding being over gross.  The Himax was designed to comply with FAR Part23 utility category load limits. The normal category load limit won't be exceeded until one is 88 lbs over the design gross weight.

Look at the Load envelopes. You won't make utility category, but might make Normal, provided you read the chart correctly.
What does the weight and balance look like?