Hello, since I cannot answer your questions, I forwarded your post to ram, the main developer of GTKG. Unfortunately he is currently unable to access the forum.
He answers: "regarding the hostiles, I think banning IP is wrong, unless there is an *expire* time put on the ban and periodic re-checks are made. Second, regarding the file sharing itself, the code has not changed in GTKG. The only thing that I changed recently in 1.1.13 was fixing an old QRP (Query Routing Protocol) bug."

From my point of view I noticed that now using GTKG version 1.1.13 the host cache for leaves and ultrapeers fills up reaching a steady level after a few days. Using the bugged version 1.1.12 instead the regular hosts (leaves) cache gradually emptied, while the ultrapeers cache filled up to the limit. This gave me the (probably) false impression that Gnutella network had too much ultrapeer nodes.