I second the advice to avoid going too much oversize. Moonshot-now-Perigee was re-rigged prior to our purchase with oversize sheets for the Headsail/Genoa and, whilst this gives confidence for the big blow, they do not fit the self-tailers at all well, requiring care (and muscle) when wrapping the sheets, and a watchful eye and re-sheeting on occasion, otherwise resulting in slippages or once or twice losing hold completely.
I will be going down a size when it comes time to replace.
Perigee, SM#396, Martinique
(not on-board, so unable to give measurements