What caused the hole?? Is it corrosion
or an old fitting that was removed and puttied over?? If the latter, wouldn't worry about it, if the former it might require further remediation to cure the cause of the electrolysis
and reinforce around the hole. In and of itself, a 1" puka is not a big deal in the strength of the mast. Racing
boats cut a bunch of slots in the mast to run internal halyards without a problem. Our mast has had a lot of hardware
added and removed over the years and the mast is still functioning well. If you think the mast needs reinforcement, riveting a piece over the puka is the conventional way to repair aluminum
. Look at long time service/high flight hour 737s if you want to get an idea what Boeing and the FAA think of how strong these type of patches are. FWIW, aluminum
welds about 25% weaker than the surrounding metal. That is unlike steel
welding where the welds are just as strong as the metal being welded.