Engine cooling

Dang, it's cold up here in South Dakota and when I fly my 415C, Ser# 504 with a C85-12F in it, with OAT's of less than 35 deg or so, the oil temp never comes off the peg (100 deg F). I can't get a clear answer as to whether there was ever a 'winterization kit' for these planes. I kind of doubt there were wind tunnel tests or CG simulations when the cooling holes in the front cowl were designed but I know that wind flow through it can be quite critical and if disturbed or altered might leave one or more cylinders with inadequate flow. Here's a picture. The small hole on the right of the cowl (left side in the pic) is connected to tubing that leads to the generator and mags to direct cooling air onto those accessories so I'm inclined to leave it alone. The one that's taped over has no such tubing attached and is open to the engine compartment as a whole. Taping it over made no difference in oil temp whatsoever. Temptation is to put a piece of styrofoam in the center hole above the carb intake which opens onto the base of the intake spider where the mixture from the carb is distributed to the individual pistons.

Any suggestions?

Chris