I have always found YETI to be a lesser effort, ultra low budget and the tranformation scenes suck.
But the Tri Pictures DVD went a long way in raising my opinion of it. It has a workable comic book vibe going for it, and a twist ending of sorts that is unique.
A big part of what made Naschy's films such an aquirred taste was the awful English dubs most of them recieved.
Prospero might not have had fun with HORROR RISES FROM THE TOMB, but I think it's one of the best. Emma Cohen and Helga Line are memorable and the some nice effects and plenty of cheesy sex and violence

You might want to give it a go, especially via the BCI dvd, as it is a steller presentation.
While I am at it I will throw in a good word for BLUE EYES...as well. One of Nascy's 3 giallo eforts, this is best of the bunch, and stacks up well against many Italian ones.