Re: In-mast furling
We've had at least a half dozen charters in the Virgin Islands (US, BVI, SVI) with Island Packets that had in-mast furling. This includes the 350, 370,380, and 420. Wind speeds probably averaged upper teens, with the max about 30 kts.
As others have mentioned, in-mast furling operation requires attention to the boom angle to assure proper feed through the slot and maintaining tension on the outhaul to avoid bunching (and therefore jamming) as the sail enters the slot. We didn't have any problems by adhering to this procedure and never had a problem unfurling.
However, the sail shape wasn't impressive: with no battens and minimal roach, it always seemed to be a bit baggy and wimpy--and these were not blown out sails. So, you pay for the convenience of rolling up your sail and reefing as much as you please, with relative ease. For a laid-back Virgin Islands charter, it was a great compromise.
That said, our own 35 footer has a fully-battened main with conventional slab reefing and requires a certain amount of effort to deal with the sail cover and sail ties. After some harrowing experiences reefing when it was necessary to go on deck to hook the tack, we went to single line reefing, with Karver blocks added to the existing main and all lines led back to the cockpit: reefing lines as well as the main halyard. This arrangement works pretty well, and takes not much more effort to reef than in-mast furling, although you have fixed reef points. At the end of the day, you still have to deal with sail ties and the sail cover. You also have to got on deck every once in a while to deal with the occasional snag when unfurling.
If we were to try anything else, it would be in-boom furling. We could keep the full-length battens and have a fuller roach and we would have an "infinite" number of reef points, but at a significant cost. The conversion would add a heavier boom, but the sail and furling mechanism would be relatively accessible. The in-boom approach would require attention to the boom angle (via the vang) to assure proper alignment of the luff and you would invariably have to buy a new main tailored to the in-boom conversion.
BTW, at least one of the in-boom furlers has a narrow strip of sunbrella that is used as a sail cover and closes the slot. Your slip mates will appreciate the lack of a low frequency "whistle" that you get with the in-mast furlers in a cross wind.