Hi TC,
Here's a link to what I purchased to replace an untidy front roller tube. This one is spot on the correct sizing to use with the original style end caps.
https://www.ebay.com.au/itm/2-75-70mm-STRAIGHT-INTERCOOLER-PIPING-STAINLESS-STEEL-MANDREL-BEND-L-610MM-AU/152999246356?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
No more rusting issues I'd say.
Also I have to ask where did you purchase the Groomer Reel from ?
Cheers,
BB.