Ups & Downs Oh my goodness, are there ups and downs!
I have done a few other sections of the FLT between Hornell and Salamanca, but usually now roam between Watkins Glen and Letchworth as our cottage is located near the Glen.
The trail west of WG is very hilly, the ups and downs seem endless. In addition, there are usually a lot of horses in the area as you get closer to Sugar Hill Rec area. IIRC, I think there are only 2 L/Ts in that area that you are planning on hiking. You'll go past Sugar Hill Firetower, which is pretty cool, but as I mentioned, there are always a lot of horsefolk there on weekends, as it is free camping, therefore it is a place to avoid. I don't know if the trail follows horsetrails or horses follow the FLT, (chicken or egg concept) either way, they tear up the trail pretty bad. It is tough and muddy on wet days (though I don't mean to discourage you)
I haven't done that entire section yet (someday). It is also fun Mtn Biking on the old dirt roads too. I recall there isn't a lot of water west of the Fire Tower, but it was around 2001 when I was there and that was a dry summer.
I am trying to recall if there were farms/cattle in the area, but I think it was another section I did where the stream runoff was tainted from livestock grazing nearby- I would still plan on a filter as primary means of getting water.
If you are heading up on the holiday weekend (4th of July) and need a shuttle, let me know, I will likely be in the area.
cheers
Rick