If you do this every weekend, I am surprised you are stressed regardless of your age.23 minutes is quite quick for my advanced age, so plenty of stress hormones which will always raise BG.
You mentioned previously that you do not eat before running. Does your BG rise on a non-run day and have you tried a similar run later in the day to discount Dawn Phenomenon/Foot on the Floor as a contributor to the rise?
And have you tried pre-empting the rise with a pre-run bolus as suggested?
Running does not cause my BG to rise but other exercise such as climbing does. By pre-empting the rise with extra insulin, I have been able to improve my climbing endurance and grade. If you are able to manage your BG rise with the Park Run you may be able to improve upon your time.
I have assumed this is something you would want as your BG rise is something you have mentioned multiple times.
Forgive my badgering if you are just repeating an observation.