had same issue when first purchased my st1300 2006.
I applied heat wrap to the headers with little improvement.
The best advice I can offer is:
invest in good quality FULL LENGTH boots! they will insulate your legs / shins from the heat.
I would NOT
recommend removing the black inner fairiing covers near the radiator or the lower ones as they are positioned to increase air flow thru the radiator
and to protect your wiring and frame from road grime and splatter....