When i stack 7135 i prepare them by removing the middle leg and bending the 2 outer legs down.
Then i put a droplet of super glue on to of the present 7135 and put the prepared one on top.
Then i solder the outer legs on to the bottom one.
And then i bend down the big tab so i can solder it to the bottom one with a fairly large amount of solder, so that it has a decent thermal path
I also did this some time ago:
What did you mod today? - #2400 by Jerommel 