I shoot woods, and currently a Javaman Falcon (very similar to the Super Shrew), around 46@27". I've searched up some threads here myself to help figure out the spine.
Ray Lyon and Ron LaClair have offered their suggestions, and those guys obviously know their Shrews. As I recall, Ron stated going 15 lbs. above draw weight as the starting point for his bows.
That would be assuming a 28" arrow and 125 grain point, I believe.
Greg Coffey recommends adding between 15-20lbs for his bows.
Of course, a longer arrow or heavier point will need to be factored in, if applicable. Also, I think Shrews made pre 2011 were cut 1/8"
before center, and cut to center since then.
For what it's worth (and I'm tuning impaired), I get excellent flight with 57/60's, around 28", with 100 grains up front (broad head or field point), also 65/70's, around 28 3/4's, with 125 BH's or 145 field points. Had a couple of test shafts 60&64lbs that never flew right, but I really think it was something about those particular shafts, not the spine. I think 60/65's might be the ticket for me next set.
Sorry for the long story, hope it'll help some. Feel free to PM if ya want.