Well then you're good to go. Do bracket exposure and development the first time. What you do is expose in strips, then cut the film perpendicular to those strips and develop those for rather different times e.g. N-2, N, N+2. Compare the results by contact printing and then you'll have the right exposure/dev combo from one test. Note that you may be printing to grade 2 or 1, that seems to be where I wind up when I do this. So you will probably want multigrade paper for starters.

The main problem you can have is highlight transitions being too fast. If your E6 film has blown highlights then there isn't much you can do to get them into the b&w film, but in some cases I like the effect (I posted some examples in the galleries)... and if you are really skilled then you can hand-dodge the highlights!