THACO = SAVE VS SPELLS

Someone out there has noticed this already... right?

Here's the MONSTER ATTACK MATRIX I'm currently using.  The values are comparable to those in 1ed, Labyrinth Lord, etc; that is, they are generally the same throughout, varying no more than one (or rarely two) points from the standard tables, but weighted slightly in favor of the mid-level Monsters.  I have not included values for Monsters of less than one HD; when it occurs I attach a TH penalty of -1 to -3, a -3 rendering high AC invulnerable to these nuisances.

HD     1      2      3      4      5      6      7      8      9     10
TH0  18     17    16    15     14    13     12    11    10    10

HD    11    12    13    14     15    16     17    18    19    20    21+
TH0    9      9      8      8      7      7       6      5      4     3      2

Why bother?  Its easy for me to use, seems to follow some sort of regular progression, and here's the bonus:
The TH0s are also very, very close to the Fighter Saving Throw vs Spells values, so I can quickly glance at the same Matrix for either value, and when in combat with most creatures, one number does the job for both!
Of course, some Monsters Save as other than Fighters, and this shortcut doesn't work!
Use these Save Modifiers for values nearly identical to 1st ed:
Paral/Pois/Death +3
Petrif/Poly +2
R/S/W +1
Spells (unadjusted)
as for Breath Weapon, this quick and easy system doesn't work... but really, how often is a Monster the one Saving vs BW?