Re: VHF Antenna Mounting: Masthead vs Stern Rail
RG-58 is not all that bad for a 35' run. You'll lose about 2 dB. Of course, better coax would be... well, better.
Personally, I would put it at the masthead with better coax. You can buy RG-213 for less than a dollar per foot. Add the cost of the connectors and you're still talking less than $50. You really can't afford that?