Thanks for your replies!
Initially I was getting a dual reflection. I solved that by inserting a piece of paper between the glassless carrier and the condenser. Between the glass sandwich on the glass carrier.
I haven't printed larger than 11 x 14 yet so I set the alignment a the mid point between 5x7 and 11x14. After I was done I ran the head up and down the column and could not see any difference in alignment.
Checking alignment was quick with this device though so maybe I will just do a quick check and shim if necessary.