I would suggest you read some more of the installation brochures, such as the 13617 Installation Guide: for the Responder® HD Lightbar Model(s): R2HD**, R9HD**, R10HD**; and then check with Whelen for technical assistance.
I have the Responder LP with Lin6 Super LED lightheads and a select six channel flasher fused at 8 amps, but an older version (R10HD) used stacked model 400 Lightheads and was fused with a fifteen amp fuse.
A warning on info sheet for the four channel ULF44 flasher reads: "This product is designed for use with 12 volt LED lightheads. Do not exceed 5 amps total current draw for each channel." Whelen Form No. 14103A (061807).
Did you part out a separate flasher to use on another lightbar?
Or were you looking at customizing a Responder LP?
I built up a Responder LP with Super LED Lightheads from HPD84. I spent a lot of money to obtain red and white to the front, and red and amber to the rear, and to add magnet mounts. (It would probably been easier to custom order the thing, with as much as it has cost $$$.)
But with the six channel flasher, there are ~forty six patterns, and the rotator feature at 90, 120, 150, and 250 rpm. I can see where these flash patterns could be used in custom modifications to some other lights.