What Fred said.
But to add: Yes, you can put a SS weldless valve on it. But the cranking the hell out of it may not be the issue. Gaskets only need to be snugged enough to create the seal.
Is the problem that where the hole is drilled the circumference of the conical does not allow a decentl flat surface for the valve to sit properly?
I use this on all three of my Conicals. No leaks
You can rotate it if you cut the tube shorter.
http://www.morebeer.com/products/stainless-pick-tube-sanke-keg-mash-setup.html
http://www.morebeer.com/products/stainless-12-comp-mpt.html
http://www.morebeer.com/products/stainless-full-coupler-12.html?site_id=5
and everything from post #1051 will create a leak free racking arm.
Then on the outside of the conical you will have a Male 1/2" npt that you can add whatever you want. I use this
http://www.brewershardware.com/1.5-Tri-Clover-X-1-2-Female-BSPP.html
and then a butteryfly valve.
If you want a "cutout" pic of all the components, I can get one when I get home.
You don't need the tri clover on the left, but I use them on all of mine. I hope this helps
Finally joining the party after a few wks of lurking and planning! Ordered one 15 gal (infd15-19) tank, nipple, 2 banjo valves (1.5" and 0.5"), female banjo cam with male threading, and banjo cam coupler with female threading. I'll be attaching a homemade yeast catcher to the cam coupler that's made from a water bottle and PVC adapter.
All this from ruralking.com for $110 shipped!! (Free shipping on orders over $99)
Can you send a picture or link of the water bottle pvc adaptor?