OK, but if you had a sail with correct .....
shape in the first place you probably would have an even smoother and faster ride. With a very flat cut as one would need for furling, you need MORE exposed area to do the same job. If the winds are steady in direction thats not a problem; but, when the winds are 'unstable', gusty and quartering the extra exposed area makes you vulnerable, utimately slows you down and can accumulate a lot of stress/strain in the rig. I think one must also acknowledge that a sail often needs sometimes to be 'power shaped' with a flat entry to sucessfully tack-through and to drive/punch/point through steep waves and help to accelerate coming out of a large troughs ... and you cant do that if that important shape/section of the sail is rolled up *inside* the mast (.... which I guess is a good case for in-boom furling if one MUST have a furler). Otherwise with an in-mast furler there is no way to reposition the draft (fore or aft) by halyard tension or cunningham, etc. etc. etc. and once rolled-in all youre left with is a 'speed shape' which limits tacking, lacks power to 'punch', etc. etc. If you sail in other than strictly inshore venues there WILL be a time that you will need the 'adjustability' that slab or other 'traditional' reefing systems can provide such as in clawing off a lee shore, fighting an adverse current, etc. or other situation where turning on the engine simply wont cut it. Sure, with humongous engines and always within close proximity of a safe harbor with an always safe entrance all the convenience of 'gizmos' will work; but, ... not always. Its not the size of the sail nor the exposed sail area that makes a sail function, its more the 'shape' matched to the conditions. You simply cant well *shape* a furling mainsail. You can adjust the amount of camber but not the for/aft position of that camber nor the all important 'shape' of the luff. Your choice. regardsRichH