Adding 2nd A/C to Coacmen Freedom Express 321

[Buzzcut]

Hi, we have the 321 Liberty Edition and I want to add a second A/C to the bedroom vent. Since it’s only a 30 amp unit, I added it’s own dedicated power inlet this weekend and wired up to the roof vent area while awaiting delivery of a 13,500 Dometic Brisk Air 2 unit this week.
I’m now worried that there may be an issue with the vent opening. Most vents are basically 14x14 (+/- 1/8) however my vent measures 14 1/2 x 15. Is this an area for concern or nothing to worry about and continue with the install?
Thanks for any replies!
Dave