Whisker pole mounting eye or track
For a whisker pole, if you know the right height, just a ring on the mast is a lot less expensive, and much easier to install. There are eyes made specifically for this available at West Marine and elsewhere, made os stainless steel. The stainless should be insulated from the aluminum mast to prevent eletrolytic corrosion. This can be done by appling vinyl tape to the eye's base and trimming witha knife. Like wise the screws should be insulated using a compound available for this purpose. If you use screws, drillingand tapping the aluminum mast, you should use s fine thread. For example, rather than 1/4-20, use 1/4-28. I prefer the far superior strength of stainless stell pop-rivets, though high strength rivets are not easy to come by in small quantities, and you'll need an industrial stregth rivet puller. The track is nice if you plan on flying a conventional spinnaker someday. Most cruisers probably won't. It will be much more expensive to mount a track and fit a car to it than simply attaching a rin to the mast. You will get some more flexibility in adjusting the height of the pole. A neat way of storing the pole is vertically, along the mast, by putting a fittin up above on the mast.
