While I DID buy those 11/16" tie rods from mopardude, I'll throw this into the mix for the tie rods.
The problem is not the 9/16" ends flexing. The problem is the standard slotted adjuster. Using a solid tube adjuster and 9/16" ends will solve pretty much all the flex in the tie rod that most folks will ever encounter.
You can buy a set of Global West tubular adjusters for $60 at Summit. That's for the pair! The $49 at PST is for
one adjuster. I've only been able to find the Global West sleeves in 9/16" though.
http://www.summitracing.com/parts/gls-adj-6/overview/make/dodge
I wouldn't personally mess with welding up a stock adjuster. While that might help some, the wall thickness of the stock adjuster is still pretty minimal, so just welding it up won't eliminate the flex problem. And, if you're REALLY lucky, you'll warp the stock adjuster welding it up, causing yourself unnecessary alignment grief later.