Yes they have been used for things lower then that. Not an awesome canopy but they work. And I'm not a canopy snob. As to vents, I'm surprised it doesn't already have them. They've been putting vents in that canopy for like 35 years. It's called a soft cell. It's an accuracy mod to lower toggle pressure. It's one or two huge cut outs in the #2 and #6 cell farther back on the canopy, like between the C and D lines. They were big, about 3 sq feet per cell.
Fill volume on the cells is really large and will take a long time to open. You are really a test pilot on gear that the BASE community abandoned a long time ago with good reason, no matter how much you modify it. I recall in the early 1980s and maybe late 1970s hearing about people doing this. It was quickly realized to be a horrible idea. Some of the canopies from that era, like the Stratocloud, worked great for slider down but they were not full on accuracy canopies. I see no reason for accuracy canopies given the current art of BASE canopy design. Interestingly, the old designs, like the Unit, etc., often had multiple attachment points and some bottom skin vents - which proceeded their introduction in the base community by almost 20 years.
Classic Accuracy guys love fine tuning different aspects of their canopies. This is 1 of the ways they old school the shit out of their gear. It basically reduces the internal pressure in the "ported" cell. Straight from PD in regards to the Zero Accuracy canopy: "2. Venting: PD has preinstalled tapes for soft cell “ports” on the bottom surface and wingtip vents on the rear stabilizers to make it easy to further enhance the performance of your Zero." "Soft cells serve two functions: they reduce toggle pressure (approx. 10%), and they improve stability in turbulence—particularly if a gust strikes the canopy from the side. The soft cell absorbs the impact and keeps it from transmitting spanwise."
P.S. I have no experience with these canopies other than what I have been told.