A Small Airplane Pilot transiting near NFL's R-4816S VFR; encountered IMC conditions and needed ATC vectors in the Special Use Airspace because of terrain and low visibility.

Narrative

Permission was obtained from Fallon Approach to utilize the corridor between R-4138A; R-4816N and R-4816S in the Gabbs north MOA. I advised Approach that I would need to encroach into the R-4816S to remain VFR; in which I was advised it was active and it would be alright as long as I didn't travel any further into the airspace. I was then cleared direct FLX. I advised I had one more area of clouds to maneuver around to remain VFR then I would turn direct FLX. As I maneuvered around the clouds and turned southwest; direct FLX; the visibility began to decrease. I had visual terrain separation; but the flight visibility was falling below VFR. Turning to the north; where visibility was less and terrain was higher wasn't an option. Turning back to the east wasn't an option as I would be flying into Active Restricted Airspace. My best option at this point I felt was to notify Fallon Approach I was in IMC and request vectors to FLX. I requested vectors due to the approach corridor for Fallon NAS I would need to pass through. After receiving two vectors I was in VMC again and was cleared on course. Contributing factors to the situation include moving too far into active special use airspace to avoid clouds in which I could not return if the visibility decreased. I felt advising of my situation and requesting vectors was the best decision due to the volatile airspace surrounding my location.