Is there anything I can do in the crossover/filter that would help flatten the response? My worry is that if a have the filter roll off sooner to compensate then the drop on the back side of the curve will be pretty severe and I'll loose the bottom end. Alternatively, I thought about crossing them over at about 60Hz. But that seems a bit of a waste.

I couldn't find actually T-S parameters for these, but one source suggested that they are essensially 40-1026A's whcih have T-S parameters of:

Nominal Impedance:..........................8 ohms
Frequency Response:........................30 Hz - 3000 Hz
Free Air Resonance (Fs) Frequency:.........25 Hz
Infinite Baffle Resonance Frequency:..................................23 Hz
Piston Area (SD):..........................0.0523 m2
Rated Power Input - Nominal:...........................................50 W
RMS Thermal Power Limit (PMAX):.......................................100 W
Flux Density (BL):.............................6.66 TM
DC Voice Coil Resistance (RE, ohms):...........5.6 ohms
Voice Coil Inductance (LVC at 1 kHz):...........................................0.45 mH
SPL:...........................................88 +/- 2 dB/1W/1m
Moving Mass (Mms):.............................61.5 g
Electrical Q Factor (QES):..........................................1.13
Mechanical Q Factor (QMS):..........................................3.13
Total Q Factor:.................................0.83
Equivalent Acoustic Volume (VAS):..........................................297.19 I
Mechanical Suspension Compliance (CMS, UM/N):...766 UM/N
Mechanical Mass of Cone Assembly and Free Air Load:.................61.46 g
Mechanical Mass of Cone Assembly Only:..............................................54.59 g
Peak-to-Peak (maximum) Linear Excursion:........................................2.90 mm
Cutout:..........................................10 1/4 Inches/28.5 cm
Depth:...........................................5 1/4 Inches/14.3 cm
Power Handling:..................................50 Watts RMS
Magnet Weight:...................................17.7 oz
Speaker Weight:..................................72.9 oz

Any thoughts?

I was going to use these to supplement some computer monitors I wanted to build, but they now seem a pit overkill for that. So, maybe I'll use them with my Fostex horns.