Well, there is wind that will come underneath the main when sailing downwind and when on a reach, the side winds will carry the foresail out over the water. I have tended to lower the sails while heading into the wind but I tend to not heave to just to keep fwd steerage. As a matter of fact If I'm headed directly into the wind, I would probably also have started the outboard.Have you actually tried it? I've been doing if for years on my C27... the wind doesn't rush under the main as you suggest.... besides your sheet controls the lower part of the sail and the downhaul will control the rest.
I 'd agree with not going fwd. . For my situation, I'd use the downhaul to keep the jib down if the winds are up where the waves may make a trip to the foredeck dicey.As far as dropping the main first..... that's another discussion... but we were talking about the advantages of the jib downhaul....I especially like it because I can drop the jib on the foredeck going downwind without going forward.
I don't mind changing course when lowering sails as I'm not usually in a hurry. In the instance of replacing the sail with another, I'd most likely keep the replacement sail down below until the foredeck is clean. So, it's two trips to change a sail. I'd also be very cautious about going fwd. in a heave to situation if single handing, the boat would swing around. If it were really getting nasty, I'd even consider dropping the anchor to maintain location on our lake. If I have another competent pilot, the situation of being underway would probably be safer.Stu's suggestion to heave to is certainly a good way to do it....but you may not always want to turn upwind just to drop the headsail... your intention may be to change headsails... a spinnaker or drifter for instance. In which case you don't need to add extra maneuvers..
One thing that I'd mention is that I recently changed out the block at the bow for my downhaul. I changed it to a newer but smaller one. That isn't so good because the downhaul line tends to kink and catch out there after the sail is down when I'm organizing the boat for docking after the sails are stowed . So, I'd suggest going with a decent sized block that is a fair amount bigger than only what's necessary for line size.