No point in having a QEV, your flow is greatly restricted already by not having a buffer tank as the valve on your main tank will have a very small orifice and you've got to wait for the co2 to boil which will further restrict flow.
This will mean your ram will be quite slow so as you say it won't be very impressive, but with good design it could turn someone over or possibly throw them over the side.
Although personally I'd just use a buffer tank, there not really very expensive it's just a small powder fire extinguisher from the scrapheap then just a pneumatic adapter.