Thanks Steve. I've been towing with it for a couple of years using the standard 21" Mallory rims but mostly short trips of a few thousand kms and it hasn't been an issue, even on B and some C grade roads.
We plan to do a lot more over the next few years with a new bigger van and I'd like to carry a full size spare. Would prefer not to have the cost of a set of 5 x 19" rims though.
I purchased a spare 21 inch Mallory rim from ECS - much cheaper than dealer prices. They seem to rarely come up in Australia second hand despite many people changing to smaller rims ... there must be lots sitting in garages just in case
I just tow on highways so no issue for me and I dont drive off road in the Treg - I borrow my sons Landcruiser for that if I need to