What kind of boat and are you racing PHRF, one-design, etc.?
What kind of Whisker pole? rigid or adjustable?
Anything that you can do to open the distance from the mast to the
spinnaker tack will be of benefit - downwind.
However, there are some structural concerns that I offer: Is your pulpit going to take the strain ?.... probably not in most cases as they are usually not set to the deck with vertical loads (large backing plates and stress connections to bulkheads, etc.) in mind. Secondly, will the pole be strong enough as you will be essentially constraining the pole at midspan rather than from the ends - different stress considerations as whisker poles and
spinnaker poles are designed for typically tension along the axis of the pole - not designed constraining or loading it from the middle.
For light winds ...... probably not a risk with anything you try.... but if the wind gets up and A-Kite starts to really lift the bow .... you can easily break/bend a constrained pole and possibly pull the pulpit free. For a boat with a strong waterline bow eye you might consider to attach a restraint from the eye to the outboard end of the pole etc. to take the strain instead of the pulpit.
;-)