There are a lot of things that matter when trying to maximize pointing ability. Some are very expensive to correct so you need to have a good feel for how much you really are willing to spend to get the most out of your boat.
In no paticular order, and assuming you have all the sails properly trimmed:
1) templaiting the keel. This will ensure you have the proper shape, and location of the lead
2) templaiting the rudder.
3) mast position, not just tuning, but baseplate location and partner location.
4) replacing sails with new (2 year old Dacron are no longer performance sails)
5) replacing Dacron with lighter laminate sails
6) removing weight from the boat
7) properly locating jib
8) fair bottom of boat
9) measure and possibly relocate chainplates
10) measure and possibly relocate forstay
11) add more crew weight to windward rail
12) on the 26, check for oil canning going upwind. If present structual reinforcement is neccessary
Before taking on any of these get a sail maker to come sailing with you, and ensure that the boat is being sailed to its maximum. The Columbia 26 was never designed as a pure race boat, and boats of its era are not known as great pointing boats. The 26 is a fun weekender, and a pretty good racer, but doesn't really have the pedigree for maximum upwind performance.