Bronica RF645 VF question

[ssmc]

Hi, I was hoping someone could straighten this out for me. The RF645 comes with a -1 diopter as standard and according to Tamron they are the only ones still available (I just got this news this morning). Despite being very slightly farsighted I have my DSLRs set at 0 and find that works best for me (the VF image and the displays are clearest at that setting). I can get away with some -ve (with eyestrain and slightly blurry displays) but +ve is just unusable.

So, for those who have normal eyesight, how does the -1 diopter work out? Is there something to do with the optical design of the RF645's VF optics that makes the -1 end up like a 0?

I would hate to buy an RF645 "sight unseen" with a standard diopter and find that it strains my eyes. I know from looking at one of these cameras with the diopter removed i.e. 0, the VF is perfect for me (this one had a +1 installed, and it was just painful) but leaving it out looks like the interior of the VF/RF would then be exposed to dust, etc. - you can see the edges of the VF lens with the diopter removed.

Thanks for any insight (no pun intended)

Scott