Last night I put the article noted at the start of this topic into use.
I inherited an old beat up 50 litre Becks keg last week.
Last night with the aid of dremel tool I cut the top out. (The neighbours loved me I'm sure, but it beat watching the Gilmore Girls on TV with the missus

).
It worked a treat. Took about an hour.
I used about 20 cutting bits though (rather than the 6 stated in the article). Maybe the cutting bits down here aren't as strong, or the Becks keg is higher grade stainless steel.
So now I have to drill the hole for the tap. I'm installing a Zymico
Weld-b-gone tap.
This will be my second converted keg. The long term plan is to use it as my mash tun and move away from the esky. This will allow me to do step mashes by adding heat, rather than adding additional water to the mash.
So, the article is a good one.
Cheers,
Doc