Well I must say this is the only mod I have been on that has this prob.
I say its more to do with the sever than the player and his net speed.
Try something new like ahh get on a Sever Pack that can deal with it instead of blaming the user for the crappy Sever.
I seen and been on mods with player up to 100 to 200 player at a time from all over the world and guise what lots of them use 56.Kb some even older and some with satellite network like me.
So having this Prob with only 15 to 20 user is a joke my friend.
No this is not a user Prob but a Sever Prob.
I bit that their is a bandwidth restitution invalid with this little prob and some one is using the bargain bin service pack to host the mod.
The Sever should not crash with 15 to 20 user fighting it out.
I know this because I have hosted bigger games on my own PC with out a prob.
So Blaming the user dos not Wash.
This is a Case of a cheep Sever pack getting over sold.