Self-service rocks! I managed to find the mistake but it's more like shooting pigeons with cannon - guess I will need some MIPS theory to move further.
So, partial HUD fix for Persona 3 FES PAL / SLES_553.54:
803F043C 7E00033C 2C4F6324 21187000 000064AC 7E00033C 304F6324 21187000
403F043C 7E00033C 21187000 2C4F6324 000064AC 00000000 04006324 803F043C
Marked values just got flipped (same behaviour for all HUD fixes, in my previous attempt I've just replaced them with codes from 4 PAL version) - aaand magically we have it fixed! The only part that I've figured so far is first replacement - going from 80 to 40 (shrinking image). But the rest is so rocket science ATM.