Jeff,

in Australia you'll find nacra F18s with two different beams (the early ones were released with a reduced beam to facilitate legal trailering), two different centre boards (iirc aspect ratio was increased) and a range of spinnaker chutes (mainly hard unless fitted after market). They're great boats and at least as fast a Hobie Tiger, but they fell out of fashion really quick. due to the changes mentioned above and also some inconsistancy in the masts which resulted in "tuning guides" being hard to use as each mast seemed to react differently.

Go F18, you won't look back.

The F18 with its self tacking jib and more refined controls will be easier to sail than your 5.8

Getting your crew to trap downwind all but eliminates going down the mine.