[ToddF]

It's our opinion that as the rules are written, an accumulator downstream of the solenoid valve is legal. If a QA answer rules this out, it is legal to connect multiple cylinders to a single valve. Just pick one with the internal volume of the tank you want, and plug one of the ports. Viola, instant accumulator. Not as weight efficient as a tank, but performs the same function.

Or, as someone else mentioned, pick a cylinder with a large internal volume and only plan to use half (or less) of the stroke. (This is actually the most weight efficient solution of all.)