With the shakespheare, be sure that you have a properly soldered PL 259 connector. There are a number of good studies which show that a soldered connector is better than the crimp on one.
In evaluating antennas, with an antenna analizer, one can determine the SWR (which varies fairly widely in the off the shelf antenna)--for the specific frequencies of the VHF radio. One will be ahead if you have matched antenna, rather than one with a high SWR. Sure it is just a cut piece of wire, but, the precise length is important, as is the junction.
Looking at several antennas which have either been broken, or have been disembled after the fiberglass got too "fuzzy" ; some antennas are built better than others.
I agree with the alkaline AA battery tray, but not as a primary power source, but as a back up. There are several radios which use either a rechargable pack, and a alkaline tray--I keep the radio charging on 12 or 110 volts in the boat, in my experience over 99% of the time, the rechargable will have the power for what you want.--but have the alkaline tray and at least a dozen AA batteries in the ditch bag. The hand held VHF, the hand held GPS, the Strobe, the flashlight etc all run on AA batteries, so that there are spares in an emergency.
Putting the 8 foot antenna another foot higher will not make a significant difference in the range. Put it where it is easiest to mount and is most secure while trailering and least likely to have someone grab it to use as a hand hold. (which is probably not on top of the arch).
I also advocate having two fixed VHF radios--having the radio on scan can miss an important call. In the PNW, we used the second radio for contact with commercial fishermen, Traffic separation scheme, or tugs and tows; on the ICW we use it for monitering and contact on the bridge to bridge navigation frequency, used by the commercial traffic. For example with a single radio we once missed a securitie call by a tug in a narrow channel. I gave mine on 13 when he was giving his on 16 and visa versa--so neither of us had recieved the other's call--and we met in the middle--not a problem with a C Dory, but it was a problem with a 7 foot draft, 30 ton, 62 foot motor sailer...I had to back several hundred yards and put the boat right next to the bank, so the tug and tow could get by...
One thing to watch for in a "Class D Complient" radio, vs a true class D radio--is that the US allows a recieve that scans channel 70 to be Class D Complient--vs the IEC spec which requires that there be a true second reciever section which is always on channel 70.