Unless you're hammering it with a really fast motor, you should be fine.  The laundry is porous, and you just need to bleed out enough air so the differential pressure shift doesn't pop off the nose early.  I usually put the vent hole just below the shoulder of the nose (or avbay) for this reason.

-Ken

Are you using shear pins?  What is your expected maximum altitude with this bird? Supersonic flight?  Any other significant mass objects in the nose?

I've not often vented payload bays, as I do use shear pins more often that not.  I have started to reconsider this a bit lately with bigger, higher flying birds that cost more.  This is due to the several failures I have had with shear pins that don't, despite testing. 

For example, do you vent your nose cone assembly (this is where I place trackers for example)?  If not, does the swelling caused by the pressure differential bind the nose cone to the upper airframe?  Perhaps not an issue in dual deployment, but an example of how designing pressure neutral airframes can be taken to extreme (?).

While vent holes in avy bays are a bit more critical in sizing (to avoid pressure fluctuations at transsonic speeds), IMO vent sizing in payload bays is much less critical.  If you have concerns, an extra hole is not going to defeat your ejection charges or increase drag appreciably 🙂

How big a chute are you using?  Your comment about it fitting tightly in a 2.75' long bay has me wondering ...

FWIW ... Bob