Yes, you can do that. I use it on telescopes that otherwise don't have enough back focus.
The magnification can get pretty high. I use a 40mm projection eyepiece with T2 adapter (GSO made, sold under various names) from Teleskop-Service. The magnification factor is around 2.5x. Interestingly, the baffling is MUCH better than with a barlow!! Also noteworthy is that the image is suddenly right side up and correctly oriented (if you don't use a diagonal prism, such as on a newtonian).
Image quality is very good, but there can be quite a lot of field curvature, depending on the telescope. The method seems to magnify the field curvature of the telescope and/or the eyepiece, plus it also seems to be quite f/ratio depending. It works really well with longer f/ratios.