I have a G8 from about the same vintage, so there are similarities. If I understand from your post, you are seeing the fact that the mount doesn't lock in altitude. This is the same behaviour as line and to my understanding is why Scott introduced the second bolt on the Altitude block after people started adding it DYI. I have never found this behaviour to be an issue as I make the altitude adjustment with the mount weighted.?
Bill Gardner?
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Pictor Observatory
Twitter: @pictorobs
Minor Planet 21350 - billgardner