I have a couple of thoughts for you.
While I have never used an Inverted L topped by a vertical, I have used each one separately.
I also found the vertical with elevated radials to be a good antenna (as well as liking my Inverted L). I ran the vertical with the feed point at about 10 feet (a longer painter's pole setup) and four elevated radials drooping down from the feed point to the top of four-foot electric fence poles.
Have you considered setting up the vertical as a separate, second antenna? You do not need the height of your telescoping mast. Getting the feed point of the vertical six to ten feet off the ground with elevated radials should give you a good 10 Meter setup.
W4HRL
Mike in Poquoson VA