Well I think this is more or less what you asked (have already checked if the weapons are shown correctly).
Sorry but I don't know how to post a patch on SF (ehm, just arrived you know...)
There was no need to modify "centre" (fortunately, because I haven't understood how it works exactly... ok, I mean, it shifts the picture I suppose, but how much?)
The modified files are those I found in the RC3... I hope there were no major changings in the RC4...
For the pistol, 2x2 and scale 1.3...
// =======================
// PISTOL
// =======================
item pistol
{
name "_9mm Pistol"
model weapons/pistol/pistol
weapon true
type pistol
category 2
twohanded false
shape "0 0 2 2"
center "2 0 1"
scale 1.3
ammo 12
reload 5
price 300
buytype 1
}
..and for the tachyon pistol: size 2x2, scale 1.1 to fit the slot.
// =======================
// TACHYON PISTOL
// =======================
item tachyonpistol
{
name "_Tachyon Pistol"
model weapons/tachyonpistol/tachyonpistol
weapon true
type pistol
category 2
twohanded false
shape "0 0 2 2"
center "1.3 0 1.5"
scale 1.1
ammo 20
reload 4
price 3800
buytype 1
}