You got it right. Sportman's gauge is located downstream from Big South, Joe Wright, Spencer Heights, and the Laramie Tunnel.
It's the best gauge we have for Spencer Heights, but you do have to factor in flows coming in from Laramie Tunnel. By the way, Laramie Tunnel comes in at the Spencer Heights takeout and is upstream from the Sportsman's gauge. Here's the gauge for Laramie tunnel, it seems reasonably accurate:
Sportsman's is located downstream from the Trading Post cabins and across the street from the Sportsman's lodge. There's a statue of a fisherman wearing a yellow rain jacket sitting on the porch and I think the building itself says Sportsman's Lodge, or something to that effect.
Assuming no flow out of the Laramie tunnel, here is a super rough estimate for flows:
2.5ft and below is low for Spencer Heights
2.5-3ft is medium
3-3.5 is high
3.5ft and above is juicin