"Our stack pack slides into a channel that is riveted onto each side of the boom, so there are no straps underneath."
Mine too. Nice & neat. There is a bolt rope
on the port & starboard sides of the stack pack which slides into the channel on the boom. Some other pointers:
You might want to consider whether the stack pack zip runs forward to aft, or vice versa, or each end into the middle. Because we have a bimini
under the boom we needed to tie a short length of cord onto the zipper so we could reach it - eventually that got caught up in the reefing pennant & got inside the boom where it jammed the reefing line.... It was a job to get it out.
When raising the mainsail
your sail battens can very easily get caught under the lazyjacks. Make sure your lazyjack lines are long enough to let you release them & bring them all forward to the mast
to hook under the cleat where you normally secure the ends. This will make raising the mainsail
much easier on those occasions when you cannot get exactly head
& raise the sail real quick.
Leave some slack in the lazyjacks in use so they dont cripple the shape of your sail.
Incorporating some drainage netting into the bottom of your stackpack is a real good idea.
Think about the bonnet which fits over the front of the stackpack & round the mast
to protect the front of the mainsail from UV. Make that nice & quick to secure using velcro or multiple straps & clips - you dont want to be messing around with ties.
We frap our halyards etc in place to stop them banging on the mast. On my boat we put a sail tie around the top of the bonnet to take the strain on the sail tie, not the bonnet material.