It’s great you were able to just flip the set of main panels in one piece, and not have to unstitch and re-stitch individual panels.
I don’t think your sheeting should mess with the drape of the sail. From the photos, it appears you are using the spanned running parrel downhauls, and if they are positioned and fixed correctly on the battens, when they are tensioned up a little they should pull the main luff up to the mast, and both luffs will be nice and straight.
I found it necessary to fool around a little with the positioning of these parrel downhauls, adjust (and then fix) their positions to get a good setting sail. After that, they should keep the luffs nice and straight and the sail positioned exactly where you want it in relation to the mast. It doesn't take much to overcome the aft-seeking pull of the sheets.
((I think my jib luff is very slightly shorter than the main luff - or maybe exactly equal - certainly not longer - so when the main luff is tensioned a little, the jib luff necessarily carries a little tension as well. Nothing like the tension you would put on the luff of a bermudan sail, or a western lug sail - just enough to ensure they are straight, and the main luff is alongside the mast).
While I was finding the best position for the halyard sling point, and getting the parrel downhauls exactly where they work best, I too found it necessary to add a running yard parrel, but later, when the rig was tuned, I found I didn’t need it any more. Now I just have a standing parrel for the yard, just to stop the yard flying too far away from the mast.
I keep a little tension on the parrel downhauls, and after reefing or shaking out a reef, they need to be adjusted again. I just have a couple of cam cleats for that. I found it necessary to have a downhaul on the boom also, but it was suffiicient for that to be just a standing downhaul – it takes up a bit of tension against the halyard when the sail is fully hoisted. It does nothing at any other time, so no need for it to be adjustable.
One trick I discovered by accident, is to find a way to arrange those parrel downhauls so they can’t run out very far, even when the control end is cast off from the cam cleat. They can be constrained so that they just slack off enough to allow the battens to go up and down. How you do that depends of your way of setting them up so I can’t explain how you should do it, but you can have these running parrel downhauls set up in such a way that even when they are completely slack at the control end, they never let the battens stray too far away from the mast. In that case, adjusting them just needs a quick tweak to smooth out any creases, and there is no urgency about doing it.
Once set up, it seems to me after that to be a very pleasant and easy rig to manage.