MS201T melting lower plastic?

[yardiron]

A week ago I picked up a great running but a little worse for wear MS200T. The saw runs great, cuts great, starts easy and idles great.

When i got the saw it had a lot of discolored and melted plastic on the bottom.
When the saw runs he bottom plastic gets hot enough to soften the plastic enough that it sags. The saw doesn't seem to overheat otherwise. I removed the fuel tank and there's a thin aluminum heat shield affixed to the plastic on the inside and the muffler looks stock.

The saw also leaks bar lube, it'll empty the tank overnight. The oil runs out he oil port and down the bar as it sits. No oil accumulates under the saw.
I'm running Stihl Platinum bar oil.

I've seen several of these with burnt or discolored lower plastic both on the bottom and around the exhaust opening. Is this common with this model saw?
The thin sheet of foil between the muffler and lower plastic doesn't seem like much to keep the plastic from getting too hot?

[yardiron]

Correction, the model is an MS200T,