While not ideal, as long as their clamped in place and don't leak at twice the pressure you're planning on working with, (assuming you're not working over low pressure) I don't see why not. It wouldn't be more than a very temporary fix in my setup tho. Fittings are inexpensive.
Must consider if it does leak, you're either losing a lot of CO2 or a lot of beer. I wouldn't be comfortable with either. If on the beer side, it could also make some serious foamyness.
