Chris, if the solder doesnt touch that means you can get pistons with a higher CR
If you really are possesed with finding the deck hieght, get some plumbers putty, and make a rope about 5/16" dia to drape over the piston crown. rotate the engine a few revs, then slice the impressed putty in half and measure..
If you passed the solder test I would just bolt it up and go, unless you really need to say you have 10.571:1 cr compared to 10.5:1