Poly Coated Keg as a Mash Tun?

[wup]

Well, its been 2 years since I brewed and I think Im ready to give it another shot. Anyways, I want to get my equipment up to par instead of half a$$ing everything. I have in my possesion 2 poly coated kegs, they are stainless inside with a coating of plastic/rubber which I believe is polyurethane.

Any idea how these would be for holding temps?
Im only doing 5 gallon batches is a 50L keg have to much headspace to maintain proper temp?
Also, is it worth running a sight glass on a mash tun? I don't really see the point of it, or maybe I'm missing something?
Lastly bargain fittings was the place to shop 2 years ago, is it still the case or has someone new came along?

Thanks and sorry for all the questions.

 

[ScubaSteve]

Search for simple brewing. Boerderij Kabouter (sp) made a sweet rig out of 2 kegs just like you have. Those things are valuable if you plan on going electric.

 

[wup]

Checked that thread out, those were quarter barrels, mine are 50L a little smaller then 1/2 barrel. Seemed like he had troubles with 110 V and thats all I have access to, so conventional propane fired for me for now at least