Repairing Hole in Mast Near Deck

[bassmanss]

I recently acquired a replacement mast for Catalina 30 Tall Rig (my current mast has a dent at the spreaders). However, the replacement mast came with a nasty access hole cut into the base of the mast starting at about 6" above the deck. It is a square hole that has been cut roughly 2.5 inches wide x 3.5 inches tall. The extrusion itself is a flat-sided oval just under 8 inches by 4.5 inches (.160" thick).

Should I repair this? If so, I was thinking about having it welded up. I realize this weakens the aluminum, but I figure this is a typical location for winch-pads to be welded on other masts. I've also considered just riveting a doubler? Maybe do both?

Can I repair this? If so, what is the best/right way to do it?