I had a 69 many years ago but doubt if I would know the answer to your question. The 69 was pretty under-powered but I think they beefed up the HP quite a bit in 70.
I do know a guy that has several Skee-Horses and Skimmers. I don't get in touch with him often but I could try to relay your question. I'm pretty sure he would know the answer.
There are three of his machines in this shot that was taken last winter in Copper Harbor.
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