What I did last year was to buy some rebar at Lowes and cut it down to
about 7 feet. drive the rebar home inside the cages. Don't be too
afraid of getting close to the plant, the roots you cut won't have an
impact on the plants. Tie the cages to the rebar.

I didn't use cages this year. Bad idea for me. The sun is a killer in
Dallas this year and the lack of shade from trimming them back to stay
on the stake is killing them.

Next year, I'll make my own cages. Or, just pull everything out and
make a big watermelon patch.