Alan,
Thanks for the advice...
Maybe a hole in the boot lid?? I don't fancy trying to cut into the roof...
As for the battery, the Civic Hybrid is a gas engine with electric assist - the opposite of the Prius.. so maybe there will not be as much strain on the battery as I was thinking..
I called Honda... the guy on the phone said "I don't have any inbformation about putting Ham radios in the Hybrid, but we don't generally recommend it"!!
But FIRST--- I visitied your web site and I'm going to read everything about mobile there before I post any more stupid comments..
BTW I was first Mobile in the UK in 1964, as G3UTY, home brew 10W on top band to an home brew 8ft center loaded whip... but the car was an old junker

Later
Dave KK7SS