I've been wearing glasses for flying aerobatics for about 25 years on and off. Most wearing RAF MK3 and MK4 helmets which clamp to your head and there's no way the glasses will ever come off - athough I did have a lens drop out of a pair once. The official glasses had very flat arms and no plasitic on the part of the arms which rested on the ears. So there's a clue - if you are going to clamp them to your head, thick arms will become uncomfortable very quickly.
These days I don't pull more than about 4g on infrequent aerobatic flights and I wear ordinary glasses with Peltor headsets which do hold on with quite a lot of pressure. I have never had a problem. It would be a good idea to use a headband though - I often consider it but somehow always seem to forget it. I always use a headband retainer for sailing.
It's the glasses/headset combination which is important. And as for comfort, take your headset to the optitians. You'll look like a prat while you try them on, but it will give you an idea. And try and chose flat arms.