Vorshlag has a rear top mount? It's not on their site. I'd be interested in seeing it, but it seems like I'll end up making my own.
There's no reason you can't place a radial bearing at the 'bottom' of the spring on the spring perch if you're really concerned about binding. And I'm surprised Vorshlag didn't offer it up as an alternative. It's less ideal because it will get dirty a bit quicker and require more maintenance vs. being built into the top hat, but might be a bit cheaper than eating the loss on selling used parts (although you'd have no trouble selling them).
I believe that's how Fortune Auto does it iirc (can't pull up their site right now for whatever reason), and I know Eibach sells standard sizes: (No 60mm I think)
https://www.summitracing.com/parts/eib-trb250
And the cheap option is just a plastic disc or two, that's how Bilstein's come and a few others:
http://www.streettunedmotorsports.co...202_744303.htm
Edit: If you're competing and care about hundredths of a second on your lap or run, it might be worth spending the money up front to make sure it's not an issue, if not you'll never notice. After all, the factory didn't bother to build that in and it would have cost a few bucks to do it in the rear like they did in the front.