Fly fishing limestone streams

The major difference between a freestone and limestone river is the fertility of the water in a limestone river will far exceed that of a freestone in most instances.  Water temperatures and alkalinity remain fairly constant throughout the year.  What this means to a fisherman is that the abundance of natural insects can make the fish very selective at times, since you are normally competing with tons of naturals.  The next major note is that many of the limestoners have wild fish, once again making it a little tougher.
 
I personally have never fished Falling Springs so I will make a few suggestions based on the limestoners I fish here in central PA.  I almost always use 5x tippet for nymph fishing and for most of my dry fishing.  But, there are times when 6x is necessary to fish midge patterns and small mayfly patterns, generally on top.  Flouro tippet to me, is really not beneficial enough to justify a cost of 3 times that of standard tippet.  However, it is good for nymph fishing because it sinks faster than regular mono.
 
For fly patterns in limestoners, shrimp, cressbugs, and sowbugs are almost always present in good numbers and the fish feed on them year round, especially in slower water.  Midges are another source present all year round, you should carry some larva and pupa patterns in sizes #18-24.  The mayflies present usually are seasonal, a good hatch chart of the water you are planning to fish will be useful.  To represent generic mayflies; hares ears, PT's and copper johns will almost always take some fish even if they are not an exact match of the naturals.  The last major group of bugs you are likely to see are caddisflies.  Like the mayflies they are seasonal in their appearances.  Carry a few elk hairs, emergers, and pupae and you will be covered for them.
 
Hope this helps, you are likely to get some additional input as well.

you can rent the under water world of trout through netflix.com very interesting dvd

pick up one of the many books written by Charles Meck--  he writes a lot about limestone streams, their structure, bug life, etc......

pa trout streams and their hatches
fishing limestone streams

both are very informative

ps....

wendell ozefovich's videos are great

the underwater world of trout--discovery
the underwater world of trout--feeding lies

the videos let you see into the world of a trout stocked/wild......
very neat

Rick,
 
In another post you mentioned you were coming state-side at some point.  Will it be in the May - June timeframe?  If so, lets get together on the Little J.