Hi
Dual-wielding two rapiers gives the same penalty as having ANY non-light weapon in the off-hand, a -2 penalty to hit with all attacks assuming you have the Two-wpn fighting feat.
Both PHB (PnP game) and TOEE manual/game help list Rapier as a medium weapon. Weapon Finesse should help offset penalties if your DEX is higher than STR.
Weapon Finesse works for Short sword, Dagger, Rapier, Unarmed Strike, Spiked Chain, Light Hammer, Light Mace and Handaxe. It should also work for Light Pick.
Read in the forum that for some Finesse & Short Sword is bugged, but it works for me.
The bonus/penalties are as follows:
Mainhand / Offhand
Dual wield: -6 / -10 to hit
Light offhand: +2 / +2 to hit
Two-wpn feat: +2 / +6 to hit
Wearing Buckler: 0 / -1 to hit
All of the above stack
Hope this helps
