Okay. I played with it. The fact is, even after fiddling with the hint brushes, trying to simplify the model and compiling my arse off
I have to face the truth. The fancy carriage has to go. The map comes first and as it's a CS map speed is everything. Bye bye carriage. (Maybe one day on the HL2 engine...)
It'd funny that the thing that probably originally inspired the map now has to go. The good thing is that without it, r_speeds are now at acceptible levels on pretty much most of the map.
I'll keep a copy of the 'fancy' map for private LAN play as it's fun breaking all the widows and stuff and trying to lock each other in the carriage and other silly stuff.