Stabilizing Impedance - Parallel Resistor?

I am near finishing a pair of Pencil 7.3s and Pencil 10.2s, will very likely end up using a sub on [whichever I prefer]. I would like to use a single series cap to limit the bass and cone excursion (and the associated nasties that go with that). The issue I have is the impedance peak on both the drivers. Seems like a cap would not be very effective if the impedance rises as much as it appears on the spec sheets.

I have a Marchand crossover that I will use as a low pass filter. It does not provide an acceptable level of quality to use the high-pass section. (I have not heard any bi-amp crossover that does. It is not an option. That is not the reason or topic of this thread.)

Would it be reasonable to use a resistor in parallel with the driver to help limit (dampen down?) the peak? Would there be any adverse impact on the sound by doing this?

My amps deliver over 150 watts so that is not an issue.
 
A parallel shunt resistor will lower the overall impedance and would reduce the resonant peak in free air somewhat. Efficiency &c. will be impacted, but it might (might) help make a 1st order high-pass at a fairly low frequency more practical. The pensils, if damped to the default level, present a fairly unreactive load as-is, so there's a slightly better chance of it working than it might normally do. As a rule though, this is not an approach likely to work all that well with vented boxes; if a 1st order high-pass is required at a relatively low frequency, that usually mandates the driver in question being in a sealed cabinet with a proper notch on it, which is not a cheap undertaking given the size of the components needed (and the fact that these need to be of high quality).