Pneumatic limit

We came across rule R11 that stated

We were wondering if this rule meant that there was a limit to the number of pistons you could use.

No; there is no limit. As many as you can plug in and pay for. There is already a thread on this topic on the forums somewhere; I recommend digging around for it. It has some nice information.

Try checking the Q&A first before posting a question on the forums. Chances are, your answer is right there in one of its threads and you don’t need to post on the forums at all.