Does anybody know - how different are compounds in ra1 tires and v70a compaund in v700 kumhos? do they behave different enough when tires warm up?

I just got a chance to buy for peanuts a set of used shaved ra1 335mm tires with may be 70% of thread on `em and wonder if it would be safe to some degree to run them in rear with new 265 kumhos in front as i have 2 sets of those.

 

From my use with both tires the ultimate grip is about the same but the Kumhos get greasy faster so I would say that is should be safe ti use them.