I overheard a station the other day saying that he was
using an AH-4 to load a 17m HamStick on all bands from
75m through 10m. I was thinking of doing the same but
using a 30m HamStick (not resonant on any ham band that
allows SSB operation). Anyone tried this? .......

It's pretty mediocre...It would be much better to actually tune
the hamstick to the different bands by changing the stinger
length.
But it would take a long stinger to tune 75m, with no loading
coil. A 10 meter hamstick can tune 20m by adding appx 2 ft
longer a stinger. A 20m stick can tune 40m by adding about 4-5
ft of stinger. I did that for a while, and it works much
better than you might think.
Myself, I always tune the antenna to resonance by using a hi-Q
loading coil. There is less coil losses, but also the current
distribution is much better, which raises the efficiency
quite a bit.
I just mounted my antenna on my #2 truck. It's even
higher than my other truck. I installed a ball mount on
the cab, about 6 inches below the roofline, on the pillar
between the back window, and my side window. The base of the
antenna is 64 inches off the ground. My antenna is 11 ft
total height, and is center loaded in the driving mode.
That puts my loading coil at about 124+ inches off the ground.
The stinger is 5 ft...Yep, it's tall, and I whack trees
o-plenty. But it works very well. I also have a 3 ft mast,
that I can add to the antenna, and have the coil 8 ft from
the base. The total height is about 19 ft.... Naturally,
I don't drive with it that tall, but use it stationary...
That antenna compared to a tuner loaded whip?
Ain't none... I'd probably be 2-4 S units louder than you
on 75m to the average person...
A friend of mine wants to run a tuner loaded whip...I can't
talk him out of it...Oh well...I'll catch him some day after
he installs it, and do a side by side comparison with my
antenna. It's gonna be ugly the way I spank his heiney on
75m....:/ 40m too, to a slightly lesser extent...
BTW, I also have a shorter 10 ft antenna , with the coil at
about 2.5 ft off the base...It's my old antenna...But I'm
gonna use it on this truck for a "heavy tree" antenna when
I'm in town...With the coil lower, it will take trees better.
But I'll use the other anytime I'm on the road. This
is the highest I've mounted a mobile so far...I'm over the
legal limit of 13.6 a bit, being mine is about 16 ft tall
total..But it sways back, so when moving I can clear stuff
lower than that. A tuner loaded whip is ok on 20-10, but
even still, the hi-q coil antenna is still that much better.
On 20m, my antenna is like being at home...I don't use many
turns of coil on 20m...The efficiency is pretty high.
MK