Going through same problems
I am going through a lot of the same problems with our Beneteau 411 except I have backstays that I don't want to cut. Shakespear makes at least three whips that will work. They are the 390, 5390, and I think the 5390R. These are in the 17-23' range and have a smaller upper section. All require an antenna tuner (about $500). In fact even the backstay approach requires the same type tuner to work across the full spectrum of frequencies. 150 watt transmitters require large 12 volt feeds and draw in the 15-20 amp range when transmitting, luckily only a few amps when recieving. I have been told to run direct from battery (with fuse) or from a very large source where that type draw will not produce a voltage drop.Read your installation manual and you will pribably find the need to ground several components and that copper strapping is recommended. There are techniques for running that (folding around corners) and terminating at connections. Good Luck.George