Yes. Clearance issues between the bearings and pipe in “middle” assembly. You will see what I mean when you get it assembled. It was only “just” touching, so you may well be able to tweak the bolts to get an extra clearance. I didn’t have success.
Please let me know how you get on. It would be great to know if 25.4mm tube is still a viable option.
FYI. The alloy tube I linked ends up being less than $4.50 per metre if you buy a full length. Cheaper than the bunnings tube you listed. But as you have already purchased the bunnings tube I understand not wanting to buy tube twice.
Good luck with the build. Looking forward to seeing how it turns out.