mainsails rarely if ever roll or furl flat. each time you furl, the Dacron cloth is being stretched. after 9 years the sail is gone - re-cutting is a waste of money
even full batten Dacron mainsails, which are merely raised and lowered, rarely last more than 6 - 8 years if used frequently.
i think it's time for a new main sail. you might want to discuss with the sailmaker
if a stronger cloth like hydra-net can be used. the woven dyneema
threads will reduce to stretch to a minimum. since it is much stronger than conventional Dacron, you may be able to go with a lighter weight (thinner) cloth that may furl better and perform as well or better than heavier weight Dacrons of comparable strength.
when discussing a new sail with the sailmaker
, ask if furling
mainsails can be fitted with "over-head leech lines".
as for vertical battens - I've spoken to some sailmakers and they indicated that added performance and durability in furling mainsails is marginal at best.
in the interim, experiment
with the all the trimming advise previously given till you meet with your sailmaker. take lost
of photos under sail so they can see exactly the condition of your sail and rig. rig tuning is very important with in-mast furling mains.