This was the obvious solution to me too, a zoom- OP even likes the square beams! But gives you the perfectly narrow focused beam, no spill, and can just slide back to all flood or anywhere in between when you want, instead of having to remove a make-shift contraption taped to the end of your light that doubles its length lol!
But the OP sounds like he is having fun with the process anyway more than anything (& nice work btw!), so that's the main thing. Just for reference, for anyone searching the archives coming across this thread's requirements, just be aware of the nicer solutions that do exactly this, just as they come from the factory. I'm totally sold on zoomables, most are great quality for the price too.