63mm bore ram. @8bar is 250 kg force.
Volume of the ram is .155liter. Buffertank size 0.45l or closeby.
A 12oz tank is 15% larger in volume. And it looks like a standard CO2 paintball bottle. Way heavier than needed for LP.

The Trevor can be adapted to be mounted directly on the bottle if you use an on/off valve for the bottle. Saving some weight and space.
I don't see a low pressure relieve device in your setup.

I would go for FP, with a 25mm bore ram. Same force, but a lot smaller and lighter.
With FP you can use a smaller buffertank, or dispence of it.
The only disadvantage of a simple FP setup is that it's single acting, and that you'll need bungees for the return.