Yes, a good check is to see what the electric field is doing at the port. Does the electric field vectors/or 2D plot look sensible? Another check is to increase the dimensions of the port and compare the results/impedance to what you got before, is the error small, if so the first port size is fine.
In my opinion, I'd opt for a port to be a little larger than to be on the small side. Just lookout for warnings when the simulation runs to make sure that there are no other modes other than what you expect.
Also for microstrip, the bottom of the port must be in contact with the ground plane but does not need to go past it.