you can set fireplus variables during the game,  as well as you can do it  from the fireplus program interface.

Console commands: 

in the game  hit  ~ (below the Esc key) key and write the fireplus console commands.


    Arena Pro commands:

SEE "fplusq3a.cfg" FOR COMPLETE COMMAND LISTING

   usage:  f_ArenaWeapon <weapon num 0-9>     0 disables arena pro
   f_ArenaWeapon 5          --> rocket arena
   f_ArenaWeapon 3         --> shotgun arena  and so on..

to set the damage:
n = the integer  value for the variable.
/seta f_ShotgunDamage  n           // n equals to any number.
/seta f_MachinegunDamage 50     //makes machinegun damage 50
/seta f_grenadedamage 100        // makes damage 100
/seta f_homing 1    // activates homing rockets (to deactivate write "0" instead of "1"

example commands taken from fplusq3a.cfg:

seta f_MachinegunDamage "7"
seta f_MachinegunSpread "200"
seta f_MachinegunFiringRate "100"
seta f_MachinegunMaxAmmo "200"
seta f_ShotgunDamage "10"
seta f_ShotgunSpread "700"
seta f_ShotgunFiringRate "1000"
seta f_ShotgunMaxAmmo "200"
seta f_LightningDamage "8"
seta f_LightningRange "768"
seta f_LightningFiringRate "50"
seta f_LightningMaxAmmo "200"
seta f_RailDamage "100"
seta f_RailFiringRate "1500"
seta f_RailMaxAmmo "200"
seta f_GrenadeDamage "100"
seta f_GrenadeSplashDamage "100"
seta f_GrenadeSplashRadius "150"
seta f_GrenadeMissileSpeed "700"
seta f_GrenadeFiringRate "800"
seta f_GrenadeMaxAmmo "200"
seta f_PlasmaDamage "20"
seta f_PlasmaSplashDamage "15"
seta f_PlasmaSplashRadius "20"
seta f_PlasmaMissileSpeed "2000"
seta f_PlasmaFiringRate "100"
seta f_PlasmaMaxAmmo "200"
seta f_RocketDamage "100"
seta f_RocketSplashDamage "100"
seta f_RocketSplashRadius "150"
seta f_RocketMissileSpeed "900"
seta f_RocketFiringRate "800"
seta f_RocketMaxAmmo "200"
seta f_BfgDamage "100"
seta f_BfgSplashDamage "100"
seta f_BfgSplashRadius "120"
seta f_BfgMissileSpeed "2000"
seta f_BfgFiringRate "200"
seta f_BfgMaxAmmo "200"
seta f_RailBowDamage "150"
seta f_RailBowFiringRate "1000"
seta f_RailBowMaxAmmo "200"
seta f_DestroGunDamage "200"
seta f_DestroGunFiringRate "900"
seta f_DestroGunMaxAmmo "200"