I would suggest the following:
Read the Thoughts of Hondaman forum, for the tips on the 500/550 there. This will get you started. Porting and spark timing on the Mid Four is seldom (if ever) done correctly by dealers and shops, and if yours has more than 5000 miles on it, there's MANY small things that can perk it up, significantly.
If you take it down, install pistons of at least 0.5mm oversize, or the 605cc kit from Cruisinmage, but contact me for some specific details about this one.
Get a Megacycle Cam, and dial it in.
Or, talk with Cameron (look up the Gentleman's Express builds he is doing): he's got some real hotrod 500/550s going lately, too. So does PJ!