It would be pretty sweet if you could have the volume tray plugin run a command on double-click. I patched src/plugins/volumealsa.c to reflect this want. I tried to stick to the formatting that I saw in the lxpanel files. Sorry if the patch file is poorly made or anything, I just used "git diff > volumealsa.c". Hope it can be lxde worthy. Not sure how useful everyone else might find this..
Diff file generated by git.
C file just in case I screwed up badly with the diff file. :)