Yes, I have a solution.
First, 'fast mode' and 'slow mode' does have an effect in multiplayer. The actual speed slider doesn't have an effect, however, that's true. The issue is that even using 'slow mode' the game will most likely run too fast, anyhow. Why do I say 'most likely'? Because this game is special in the way that the speed of the game is directly dictated by the speed of the CPU. Also, the game will try to sync to the slowest CPU in multiplayer.
What does this mean? Well, if the game is still running too fast there's only one solution; and that's to slow down the slowest of the CPUs further. This can be done by down clocking the CPU through the BIOS, or using Intel Speed Step - or the AMD version - if such is available. If so, you can set a CPU limit through the Power management in Windows. Aim for around 1200-2000MHz in either case using 'slow mode' (in-game).
So, will this make the game run perfect in multiplayer? No, but a lot better! Playable, yes.
Why not perfect? Well, because of the syncing done between multiple PCs with CPUs that's not equally powerful, and just the fact that game is super sensitive to any change in available CPU power. Like, if you move the mini-map in-game by dragging the mouse around in it, the whole game down on all the PCs connected to the game!
If you had a couple of the same kind of PC with the same specs (CPU mostly important) and at the right CPU speed, in terms of translated game speed, it might run close to perfect, as close it can come, anyhow. Having the same CPU speed (actual CPU performance) across multiple PCs might simplify the syncing between the PCs. However, I just tried with a 4.2GHz and a 1200HMz (down clocked) and the game ran pretty fine. Not perfect, though. There was a tiny bit of micro stutter (syncing, likely). But perfectly playable. Using the mini-map, as said, uses enough resources to slow the game down. Therefore try not to use it too much in-game.
The short answer is also that the game just wasn't really designed for multiplayer performace (yeah, it's a bit sad) , however, I hope somebody will benefits from this information.
Post edited November 03, 2012 by hippox99