There are no SPCLxx's in BG1, so it must be the .2da. Yep, just checked and it is .
Indeed i have amended my Lay on Hands spell SPCL211 and it works fine with no Appending to the 2DA file.
Also I have gone back and looked at the Lay on Hands spell in BG1 (SPIN109) and it is set up the same way as the SPCL211 except it only goes as far as level 20 so i would assume that the 2DA is obsolete in BG1 aswell!
On a side note they did update the layhands.2DA between BG1 and BG2 as in BG1 layhands started with 2 points at level 1 and in BG2 it started with 2 points at level 2. The spells updated reflecting those changes too!
Perhaps Layhands.2DA is used for something else? Anyway it seems to obsolete in both games.
Perhaps this is something that should make it's way in to the IESDP (alongside each 2DA perhaps it could say if it is obsolete or not)!