Digital BW, The Print

My densitometer arrived today without calibration plaques.  I have a 
Kodak Q60 (IT8) reflection target.  I was able to locate a web site 
with densities for the gray scale on the bottom, including averages 
for the d max and d min from 16 different charts they had tested.  
I used these values and calibrated the densitometer.  Based on this, 
I am getting readings that seem reasonable.  (EEM 1.64 dmax and HPR 
at 1.72)  
Is this a fairly accurate way to go or should I bite the bullet and 
buy the calibration plaque.  I will be using the densitometer to 
build curves with QTR or IJC/OPM.

Thanks,
Peter