Honestly, I get left turners pulling out at the last minute in the pickup much more often than when on the bike. I don't bother honking the horn, I just let off the gas a little and then continue on. (in the truck)
I believe the reason is that I can't really weave in the truck like I do on the supermoto. So I think that even with even a large profile vehicle, speed can not be judged accurately.
I always drive and ride a little faster than the speed limit, and on the bike I'm always riding to distance myself from the traffic around and behind me.
That puts me in a position (on my own) where I need to make myself visible. I stand when cresting hills, and gently ride back and forth in my lane most of the time.
The nano-second I see a left turning car appear on a side street, or in a center turn lane, I swerve towards them, and then back and forth a few times as I close in.
It's far from a smooth subtle weave, I push on the bar hard, it's an abrupt change of direction, followed by more of them.
My headlight beam is doing a figure eight (fork mounted) so it's flashing around like a search light, just not a very bright one.
I've had people start to pull out that could have easily made it. They then do a "I'm sorry" wave, and it's returned with a "no prob, thanks for waiting and not killing me" wave.
It is the changing of profile and direction that allows our speed to be judged more accurately.
More lighting is always a good idea if it doesn't blind anyone.