First build ,cat D11

[Lmackattack]

Aluminum for pistons are fine as long as you can keep it from making contact with the tube.

I built race car dampers for 10 years and the dampers were made with aluminum or steel tubes with aluminum pistons.

Some pistons had just 2 grooves cut for a slide ring and an o ring. That's all that was needed to keep fluid from snaking past.

The cover for the rod to exit thru can consist a few ways. Use of a single x style oring can be used with limited seapage past the rod, most dampers i built had a backing oring with step seals and dust ring. Thesis more complex but less dirt can get in...

If you have any questions I will gladly help..