Do any classes outlaw it?
None of the Hobie OD classes allow it - but a Tiger racing as an F-18 could. The round boom on the Tiger isn't strong enough for it, but you could do it with the old, rectangular boom.
Actually I think the Hobie Class does allow it. We went through this drill at the Hobie 16 NA's in Rhode Island. One of the competitors had a sort of mid-boom sheeting that was closer to the gooseneck than mid-boom. At any rate, we wanted to make sure it was legal before racing started so we looked into it quite a bit. It was decided to be legal at the time.
14. BOOMS
14.2 Boom bales for the purpose of hanging mainsheet
blocks may be added, deleted or relocated.
16. EQUIPMENT
16.4 Main, boom and jib sheet blocks of different design
or make may be used provided the purchase
advantage remains equal to or less than
7:1 on the mainsheet system and 3:1 on the jib
sheet system unless specified otherwise in individual
boat class rules.
