Eureka! I grabbed md5sum and ran it on the file I had downloaded earlier:

md5sum -b v151.hijack.v200b8.mk2.zImage
a84823f817058ab8994d701616290099 *v151.hijack.v200b8.mk2.zImage

Then I used Intellitamper (www.intellitamper.com) to download the 1.51 kernel directly from the Hijack site:

md5sum -b v151.hijack.v200b8.mk2.zImage
3bca07933c8a23ab5dee7cb68a7563b9 *v151.hijack.v200b8.mk2.zImage

I uploaded it with LogoEdit, and it works great. Thanks for the tip.
One last thing...are there any detailed instructions for using the Hijack kernel? I can find a feature list on the home page, but with so many addons, it seems strange that I can't find a readme or docs anywhere. Does everyone just play around with it until they know how to use all its features?