How many...

"situation where I'm fighting a fish for 20 minutes in a crowd or have to constantly break bigger fish off. "
 
 
I would say if you fish a 5wt thats what will happen, plus if you plan to release the fish it would be best not to fight them to exhaustion

Wait till december
Chris

I fish nothing but a 6 wt. right now and drop to a 4 wt. in December.  Pa streams do not require any thing more.  If I go to Ohio, I will go up to a   
7 wt. and NY will normally require an 8 for the Kings and larger steelies.  If you hook the fish in the mouth, rather than the side/tail, they fight for 5-10 minutes tops.  As for fishing in the crowds, that will be your own decision to make.  Tight Lines. 

ronnie,
I fish a 5wt quite often up there.  Never seemed to have a problem...as griffon said a fair hooked fish is no problem on a 5wt.  If your going to use a 5wt stay away from the really fast rods because they dont offer any tippet protection.  But, I think you will be fine....Ive fished my buddies legend ultra 4wt for trout and based on that I think the action would be great for steel.
 
Chris

When i was up this weekend...i only used my 3 weight....just like bigsteeljack said....you just have to pay attention to fish at all times.  It can be alot of fun...i usually use a higher pound tippit and you don't have to fight the fish to exhaustion if you just know what your doing.  but i wouldn't try using a smaller weight rod around alot of people...the fish goes where it wants to go....just my input.

I generally use a 6wt 9' rod and have no problems with the steelies.  I just bought a 7 wt and it works fine as well.  I even have caught steelies on a 4wt.  The things to keep in mind are the type of fly, how much weight you are using, the water flow, and the time of the year.  When fishing for fresh chromers say near the mouth of the streams where they have plenty of water to run around in, you might want to go with the higher weight rods.  I have had some of these fresh fish that were like a freight train.  Some take off like a shot and it is nearly impossible to stop them and others that run a little and roll right over. 
 
When the water is high and fast, the fish is not the only concern, you also have the current to think about.  Here you might need more weight to get the flies down and a bit more backbone on the rod to fight the fish if it decides to put its head down in the current. 
 
One other thing to keep in mind is the power of the rod.  I am no expert on fly rods, but the line wt is not the only consideration.  I have two 4 wt rods.  One is for small stream trout ONLY and the other will handle steelies.  The difference is the construction of the rod. 
 
Bottom line is use what you are comfortable with and will enjoy and can handle the situation.  As a confessed equipment junkie, I firmly believe you can never have too many rods and reels, that way I can justify buying a variety to meet any conditions I may encounter....  Besides, it is always a thrill to catch your first fish on a new rod...
 
Good luck...

After holding someone's Sage eight weight at the river a while back (can't remember which model it was), I feel justified to buy a new one. It was about half the diameter and weight as my Premier. Problem is convincing the wife that I need yet another one.

Now that I think about it, while the five weight LU is no Z-Axis, it's not exactly 'slow' either. In other words it's one of the faster rods I've fished so I think I'd be a little concerned with tippet protection...

I haven't fished my Legend Ultra three weight because I've yet to purchase a reel for it, but I can't wait to fish it. It should be a perfect Cool Spring/Neshannock Creek rod.

By the way, didn't mean to sound like I'm fishing the Stop Sign hole or anything exclusively (where all the crowds are). I just meant that, well...from what I've experienced first hand...relative solitude, fish on and suddenly four or five anglers move in from out of nowhere. I've been fishing around Sterrettania with no one but my buddy in sight and had anglers beam down from the clouds...atleast that's what it seamed like. So when I say crowds, that's what I meant. Typically I try and stay away from the lower reaches if I can help it.

I used my 5wt up until this year, i will be using a new 7. I really think the action plays the biggest role. If your after the sensitivity try a slow action rod. Both of my nymph rods are the slowest of the slow. I never understood why guys want these stiff 8wt rods when they end up using 4x tippet. Let the rod absorb the shock!

Yes, go cast them before you buy one.