What is interesting is that once SYN3 came out, it was recommended for the Primary/Trans on the sporty (20w-50) yet at least on my 09, they have gone back to recommending Formula+. I was under the impression that Formula+ was a 75w-90 gear lube.
With regard to it being heavy, based on the viscosity of a few oils that I pulled, it looks like 20w-50 motor oil is about the same viscosity as 75w-90. Comparing AMSOIL 20w-50 (MCV) and 75w-90 (SVG) the 20w-50 is actually heavier.
SAE 20W-50 Synthetic Motorcycle Oil (MCV)
Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 20.56
Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 152.0
Viscosity Index (ASTM D-2270) 161
SEVERE GEAR® 75W-90 (SVG)
Kinematic Viscosity @ 100°C, cSt (ASTM D-445)16.7
Kinematic Viscosity @ 40°C, cst (ASTM D-445)109.1
Viscosity Index (ASTM D-2270) 165
Kind of sucks with the Sporty that the primary and trans are stuck with the same oil supply.