I'd just pull one end of the lower hose (I did the rad end) and get that thing inside... although looking at your pics, you seem to like the cold Once it's inside and accessible you have many attack options to get it out. When you say the screw is stripped, you mean the head, correct? how 'bout small nosed pliers or small nose vise-grip? I have had success cutting a slot with a small cutoff wheel in a dremel. A drop of Kroil sitting overnight can't hurt either...To me a gallon or two of coolant is worth getting the dang thing inside out of the cold...but that's just me, I'd rather sweat than freeze.