Ohlins Novice Seeks SBK Fork Specs

[hillbillees]

I'm looking at some 1098 Ohlins FG511 forks for my project '06 Sport Classic 1000 Sport
I know 53/56mm will require some messing around with my 50/54 triples and the radial brakes upgrade is fairly straightforward with lots of info from a search on this site

I'm happy with the FG332 Paul Smart Ohlins on my road '06 SC but the project bike will be used on the track so I lust for something better
Where I'm getting stuck is.....I think I've worked out that the FG511 is a far better fork than the FG332 but the more I search the more I get lost!
Please correct me if I am wrong...
The FG511 are Road and Track forks?
They have 25mm valves? I have seen ads for 25mm upgrade kits for 1098 forks so I guess the standard valves are replaced to improve the older style forks

In my quest for Ohlins knowledge I now discover that I can get new, custom built FGRT815 (53/56) or FGRT819 (53/53) forks for $650 more (plus $$$postage and taxes) than the used 3000 mile FG511 forks I am looking at.
Is the lower fork triple diameter the only difference between the two forks or are there internal differences?
Do the 56mm fork lowers provide any improvement in stability?
How much better will these forks be than the FG511?

Can someone offer advice or point me in the direction of where I can read the information about the differences in specs between all of these forks?

Looking forward to many words of wisdom

Cheers
Kelvin