Sounds right. I have a similar container with a Clematis on a 6'trellis and it looks ver balanced. Make sure you anchor the trellis. I drilled two holes in the bottpm of the pot for the ends of the trellis and attached a wood block at the soil surface to attach the trellis.

Good idea. The pots are 16" deep. Perhaps it won't be necessary to drill, at least I hope not, since they have already been planted.
Robin

I've never drilled holes to hold the trellis up. I have had to replace wooden ones often so I now use the steel types from Walmart and others.

You can weave the stems in and out if they get wild.

Penny

Lowes has green metal trellises that are 6'high and 18" wide. They are presently on sale for $6.47. Bought 7 of them for my new pots.
Robin