Riley folded up several years ago. Their website was up for a couple of years after they ceased doing business. I once chatted with an owner o a Super, and he normally cruised at 188 kts., at altitude. There was a picture of him, and a travelling companion, on his blog site, over Iceland at 21K. The 520's had a terrible reputation for cracking cylinders. Keeping the temps up during descent was critical for engine longevity.
That's about all I can remember about the Super Skyrocket. There is no longer anyone who can build a new one for you.
As an alternative, you might consider the modified airplane that Owen Bell is producing. It has TIO550's, and it does move along very well.
I had the opportunity to fly his demonstrator earlier this year.
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