Scott,
I have used an R8. Had to replace the tires with solid tires but that has turned out to be ok. I used it with all my keyboards, Roland, Korg, Yammie and now the SD7. Love it.

Regarding Cases: I had a company called Blue Heron custom make cases for both my Tyros 4 and my SD7. They are light weight, but well padded gig bag type cases. They will make them to your specs. Not cheap, but plenty worth the money. Keeps me from having to deal with extra weight of an oversized case.

Deane