Burmudan vs Gunter mainsail cut and dimensions

Is the cut of the main different for the different masts? The Gunter rig mainsail distinctly narrows above where the gaff is rigged and looks like it won't work for a straight luff. At the moment I don't have a burmudan mast to compare. Thanks

The mainsail is, so far as I'm aware, supposed to be the same shape. Where it comes out of the gaff, it should continue down the same line as if the edge was still contained inside a mast track, so when you transfer it to a bermudan mast it is meant to follow the same line. Newer sails may lack the eyelets for the lacing though, and I have heard about some old sails not fitting the bermudan mast, probably because that lower part was never designed to be hauled into a track. This may mean in practice that you need a new mainsail when you switch to the new masts, and you will need to retain the old mainsail if you're going to go on using the old mast and gaff (which can suit some locations better if there are lots of obstacles to get the thing under on the way to the water).