Geoff,

On my A2, the mainsheet goes to the end of the boom and sheet tension also forces mast rotation, the rotation being limited. This mast rotation control is very important to tuning the A2 rig. The mainsail is attached to the boom and allows outhaul adjustment independant of mainsheet tension. It all works pretty well. Personally, the mid-boom sheeting systems felt awkward when I tacked because I have always had mainsheets that went to the end of the boom or mainsail. Others swear by the mid-boom system. You see about everything on the A-Class cats.