From what I have read it seems to me that even 1 degree will influence the views dramatically but it seems to be mainly due to the boundary layer that a warmer mirror generates.
From this I think the diagram at the top of this thread is a beauty as the fan will cool the mirror over time BUT disrupt the boundary layer immediately. I'm changing the setup on my scope to be just like this and give it a go, can't do any harm but will probably improve the performance of the unbaffled fan I have at present.
Problem is its the first clear night for ages and my scope is in pieces and the mount is a disaster
Good thing I still have the binocs
Cheers