I think most alloy masts of that era had an E section.
Type I mast was tapered towards the top and the mast was sealed in an effort to prevent inversion and halyards ran down the luff groove.
It also had an adjustable gooseneck, so no Cunningham was essential.
Type II mast was similar but not sealed. The gooseneck was fixed and halyards ran down internally within the mast.
As your dinghy is 1980 vintage, then it probably used this mast.
I don’t think just lengthening the spreaders will overcome the problem. The spreaders will need to be angled further back to exert more bend pressure.
Any bend is measured by pulling the main halyard tight against the mast next to the gooseneck. Now measure from the back of the mast to the taught halyard at spreader height.
You are aiming for a gap of one and a half inches.
When rigging, stand the mast in the dinghy with the shrouds in position. The mast should be up against the heel pin but without the tabernacle pin in position.
You then apply the required tension and rake.
Does the tabernacle pin fit the hole without touching the sides of the mast.
If not, then the heel pin needs adjusting.
(New edited version………thanks Colin)
If the pin hits the back of the mast…………move the heel pin back.
If the pin hits the front of the mast………..move the heel pin forward.
If the holes in the mast foot give too big adjustments, then use some spacers such as a 5p piece.
Don’t forget, if you make any adjustment to the spreaders, then the whole rig will need to be adjusted and measured again.