Aluminumn questions, flanges, baseplates for bell jar

[Nanos]

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0095191877

I wonder how suitable this would be for making flanges, 24mm thick enough ?

I've two stainless steel half spheres that are 120mm in diameter, could I use them to join those together ?

From a brief look online it looks difficult, but not impossible to join this with stainless steel, thoughts on that ?

Also, I wonder if a large enough piece would also be suitable as a baseplate for a bell jar ?

I could possibly electroplate it with copper couldn't I ?

If I was to use it as a baseplate, how much left over distance at the edges should I have between the edge of the bell jar and nothing, couple of inches ?