Okay, I guess I understand what you want to know. I did the following steps.
Note: the confocal relation Zr = pi * wo^2/(lamba/n) = L/2 gives us almost the same optimum waist.
I thought we cared about satisfying the confocal focusing parameter, that is to say we want to set Zr = 2L_crystal. If Zr changes inside the crystal, this is the number we care about..isn't it NOT the waist size, but the rayleigh range we care about? I am not entirely sure what youre response is saying you did...
I guess the waist size would also let me know - are you using 69 um or 53 um waist size?