I had my guitar instructor set up my Strat about 2 weeks ago and it is the best set up ever.
I have the Callaham block and saddles put in. My instructor set it up with a floating bridge and only 2 springs and no matter what I do I can't get the Strat out of tune. It is truly amazing. I can pull up on the whammy bar or do dive bombs and it still stays in tune. The action is perfect and having the Callaham block put in really adds a lot of tone to the guitar. It's awesome. 2 springs with a floating bridge really works well for me. That's without having locking tuners in either.

Thats what a good setup will do. I could not tell you how many time I have heard that said. It amazes me how people think there guitar plays nice but then when they get it set by someone who knows what they are doing they are shock at how much better it becomes.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.

Thomas Jefferson

Wow only two springs? amazing!! I couldnt get any of mine to work with only 2 so thats cool congrats!

I imagine the claw screws are really cranked down.

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James Burton Upgrade Telecaster
Hot Rodded Am Fat Strat Texas Special (now featuring Kinman Traditional II pickups)
Fender Blues Jr.
SWR California Blonde
Pedals Pedals Pedals

BigJay: Thanks for volunteering to say this. People too often associate a "locking tremelo" with "locking tuners". Good job - You can go home early today...

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What's a Callagham block? Is it a replcement for the heavy die-cast alloy thing that has the the bridge bolted to it at the top end, and the trem springs at the bottom?

What advantages does it confer?

Actually the Callaham block can have a positive effect on tuning stability. I would imagine that the Callaham block would have a higher level of finish than a stock unit. One friction spot on stock Fender blocks is the holes where the straight end of the trem spring inserts into the bottom of the trem block. If the stock Fender unit is like most, the trem spring can hang up on a rough edged insert hole, causing friction as the trem and springs are moved. The blocks that come stock ususally have some pretty rough edges that need a little attention to smooth out. I will go into those 5 holes and deburr the edges and up a little into the block giving nothing for the end of the spring to catch on. I would hope the Callaham block would have this same smoothness inside the block holes from the factory.
Also, a little lube at the block holes can eliminate friction, little as it may be. I know it sounds kinda nit-picky, but we are talking minute differences in tension that can cause tuning problems. Anything that moves in the trem system must be smooth, lubed and free of as much friction as possible.