This is not going to be the typical "which saddle should I get" thread. Promise.

About me: 242lbs, 6'1", 110mm sit bone width (center to center), currently riding Selle Italia Flite Gel Flow Max saddle (150mm wide)

The Story
I rode 32 miles yesterday. My longest distance to date. Saddle felt great (normal sit-bone uncomfortableness) until the last two miles or so. It got really uncomfortable then. My previous "long" rides were 16-18 miles with no problems. This morning I barely got through 8 miles and had to get off the bike from sit-bone pain. None (or barely any) of the discomfort is genital numbness. It's all in the sit-bones.

I also have numbing on my left side, from sit-bone partially down my hamstring.

Could it be that I just need more saddle time for the pain to go away? Is it possible that the hamstring numbness is from a too-wide saddle pinching off the blood flow to the back of the leg?

I am thinking of going to a slightly narrower saddle (143mm), specifically the Romin Evo Expert. My hopes are that this narrower saddle will relieve the hamstring numbing, and still give good sit-bone support. According to the Specialized charts, this is the width I should be on anyway.

Is narrower the way to go? Is my head thinking about this correctly, or am I all whacked?

Thanks for any advice you all can offer to this newb.