I have tested HST 124's in both my current Shields with no issues and one of those is a Ported PC. It is the defense round I carry in all my 9's. As far as issues with the porting when firing I have shot mine from every position I know. I did not shoot with the gun directly under my chin.
Other than feeling a little heat at the upper chest tucked position I did not experience any difficulties or discomfort.