I thought about that approach, using a length of 1x1 for the upper leg and then a similar length piece of 1-1/4x1-1/4 for the lower leg with various holes drilled. These two would nest/telescope and then would be held in place with snap pins.
I don't think there was a big reason I ended up where I did vs your approach. You do get more adjustability with slightly more weight. In hind-sight maybe I should have done it that way.
Here's a link to an aluminum sizing chart
that I found really useful when trying to figure out what nests with what and then I went to the aluminum yard and tried a bunch of pieces to confirm.