I dont consider many ULDB ocean racers I have seen to be seaworthy but
that isnt the question. Since I happen to like the Mac26 concept, I
wonder if it can be modified to be seaworthy. I also cannot resist
any temptation to experiment. I confess, I have never examined a
Mac26 up close.
Upsize the winches, no biggie as winches of all sizes are readily
available surplus.
Better sails is no biggie as good second hand sails are available.
The CDI furler is fairly good for that size boat (PS review and my own
experience).
Smaller cockpit by filling it with extra water and fuel properly
fastened down.
Better cockpit drains retrofitted (almost all boats need this).
If it has a cutaway transom, put a cover over it.
Lock down bottom hatch boards so they cannot be removed.
Back up any deck hardware that looks insecure.
Jacklines
Check into hatch security
eliminate thru-hulls
Look into security of rudder
Security of centerboard
Knowing nothing of her rigging, I can say nothing except I get the
impression she has small sails so perhaps her small rigging is ok.
I cannot evaluate the hull construction except for what PS says which
seems ok. However, I will note that fibreglas construction has
advanced so well that today making a very good hull is easy. A
lightweight hull today can easily be stronger than a very thick hull
of yesteryear.
Any other ideas?

BTW, a web site I checked said a Pearson Triton had a much worse PHRF
than the Mac26, I dunno.

I used to know a homeless guy who lived on a trashed out Venture 21.
He lived on it and cruised all over this part of FL. He did more
sailing on that gawdawful boat than I did on my S2.

A question, is the Macgregor of Mac26 fame the same Macgregor who
built large multihulls?