I only fit sleeves to prevent any lube migrating from the spring.
A correct sized spring and a set of delrin guides, coupled with the rifle being set up correctly should remove ALL twang.
On a traditional (even home made) sleeve, the end that goes to the front of the piston has "teeth" that are bent over. This enables the spring / top hat to keep the sleeve in place.
If you're considering a tube, you'd need to bond it to the inside of the piston to keep it in place.
I'd say a complete waste of time.