I prefer to avoid using guides and stops with 0" gaps for purposes of getting the pipe or nozzle loads to pass for a few reasons:

1. Requiring them means that your model is relying on a stiffness value of 10^12 lbf/in in order to get your pipe or nozzle to pass. Your structure generally cannot meet that promise.

2. Implementing a 0 gap, especially bidirectionally, means that your system can't reliably move back into its original shape after a cycle. Metal heats and cools and will get stuck in place, and not slide, generally as your model promises it will.

3. It's impractical to build and put into place.

What is your opinion on the matter?