I once bought the plastic betta hammock for one of my Giants (just to try it),but he never used it,probably because of it not being wide enough.In his tank at the same time though is his homemade leaf hammock (which I make for all my Bettas) made from using a large soft leaf off one of the silk plants and
held by a suction cup with clip.For my Giant boys though I place two silk leaves on top of each other for more support & they love them.Maybe you can try that?
Mine is too big for the hammock. I floated some anubias and he seems to like hanging out in it and swimming through it. He actually likes to hang out at the bottom in his pots even more, that's where I always catch him resting. Maybe try a terracotta pot for your big guy.
I have a leaf hammock for my betta and she loves it. Sometimes my ADFs will use it as well. Every once in while I'll catch all three of them on it at the same time. I want to get two more for my frogs so they aren't so cramped to one leaf. My leaf is all plastic and so far I've had it for a year and seems to be in great condition.
So I decided to try just the plain one with wire support. It took him a couple days to get used to it and now he sleeps on it diagonally for some of the time. I still need to play around with the height.