Rebuilding the First & Second Stage Piston on a YH

https://m.aliexpress.com/item/32853041828.html

Here is a starting place. There is a heavy duty first stage piston, has a heavier top where they crack.

That link did not show up in usable form on my computer so here is another.

https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20190905181055&origin=y&SearchText=yong+heng&switch_new_app=y

My YH has had about 6 hours of run time and the only thing I have replaced is the check valve O ring at the high-pressure outlet. I have replaced the low-pressure piston with the new version which has got a thicker top hence stronger but that's just a precaution, the original piston is still in good shape. 

The only essential thing I have done is to clean the reed valve at the top of the high-pressure cylinder. Greasy stuff has accumulated here preventing the reed valve to close completely. Note that there are two reed valve blades here, one on each side of the center block of the cylinder head. The picture below shows the center block removed from the cylinder head and one of the reed valve blades. 

 

I couldn't find any piston that was heavy duty listed. Are all the new pistons that way? Also don't know if someone hacked them but they have broken pistons listed for sale too. Maybe somebody changed the pictures?

I'd to put one of the new pistons in mine preemptively.