Performance loss + astronomic ping after earlygame

[B.62]

my problems with running spring just wont stop....here s the latest :
playing small maps with 4 players max is fine . but when i m playing a map of about the size of deltasiege(normal) or bigger with more than 4 players after about 15 minutes it first starts to lagg and fps decrease rapid and a few minutes later my ping beginns to raise...last time i had a ping of 8k ms when spring crashed.
my connection is fine (dsl 16kdown/4kup) and my hardware should cope with spring. i use a p4 1.8 with a gf4TI4200 and 2gb ddr3 memory. and the graph setting are allrdy damn low. it cannot only be the increasing number of unit causing all this right ? and why in hell does my ping mess up like this ?

[LordMatt]

GroundDecals --> 0