You can Doug, but at the sacrifice of f ratio. For every doubling of magnification you will increase your required exposure time by 4. You can use a 2" 2X (or higher - 5X
25X exposure length) barlow or powermate (negative projection). You will just need a T thread to 2" adapter.
The other way is to use a good quality eyepiece and try positive eyepiece projection, as you have already mentioned.
Realistically though to get a reasonable size image in a respectable time you need big aperture and long focal length. i.e 12" newt @ f5 = ED80 x 2.5 and less exposure.