I say no problem since your only checking for leaks but I would purge the air out befor you turn it upside down. If you put 3-4 psi on the keg to purge te air out first then spray with a little starsan you will see bubbles if it leaking. Then release the pressure then add your priming fermentable.
Carboy's Raspberry wine, pale ale
Kegged Cooper's Stout, Coopers lager, Newfie dive bomber pee
On tap Cooper's lager, Cooper's Stout