Hi Aaron,
If you are going to use active feedback, for the highs you could start with 22nf or so in series with a 5K pot. For the lows, try taming the head bumps by dampening them with a parallel value around 200K.
For passive feedback, look in the Bottlehead website for Doc's tape mods to the Seduction preamp. Again, I'd suggest using a pot to aid in in "tweaking" the HF response.
And good luck!
Charles