In fairness I loved using my RS20 with the 128" Firehawk G3 (high contrast gray) I had in my last theater. Blacks stayed exceptionally black, and the screen did a great job of rejecting side lighting from my side windows (black out shades, but no channels).
Still, now I'm using a 124" diagonal Stewart Studiotek 130, a white surface, with 1.3 gain. Guess what? I'm still more than happy with the way my blacks look (btw- the 124" is a 2.35:1 aspect ratio, so when watching most movies, my new screen is about 2% larger than the old Firehawk, but for 16:9 viewing it's a good deal smaller than the old screen.
The better your room, the better the experience. You don't need really dark walls, floors and ceilings, but they will make a real difference in mixed scenes, in terms of blacks.
But, I digress. Keep in mind the lower lumens of the RS60 compared to older JVC's. Seems we've lost a good 25% or more compared to older models (or the new RS40).
My new room is better than my old, with its much darker walls, floors and ceiling (all dark blue or black), thanks to that the lower brightness still will do a good job for movie viewing on my 124" Cinemascope screen (no, not using an anamorphic lens). I'd be very concerned with a lighter room, and that sized screen, because of the lower lumens, Even if I found the RS60 satisfactory brand new, in my old theater with the 128", I'm pretty sure I'd be unhappy by the time the projector has 500 hours on the lamp, and probably lost at least 25%-35% of brightness.
Bottom line for 2D - enhance the blacks if you really must, but mostly, for screen sizes larger than say 110" diagonal, you'll be trying to preserve brightness, unless your room calls for a high contrast gray screen.
For smaller screens, say 100" diagonal or less, you've go t more choice, because for 2D, you'll have plenty of brightness for movies, (though sports are another matter, of course).