Stainless steel antennas are strong and durable, they are light and simple to tune but can be very hard to cut to tune you may need more than a pair of side cutters to tune them. Steel is not as good radiator of energy than copper is (copper braid covered fiberglass antennas). Also stainless steel antennas are usually longer than tuned fiberglass antennas on the same frequency. Stainless Steel antennas have a 95% efficient transmit bandwidth of around 4MHz of the 118 to 136MHz Airband, It is important to tune the antenna to the most used part of the Airband, e.g.: If you tune your steel antenna to 124MHz then it will work from 122 to 126MHz at 96 to 100% efficiency and then will gradually reduce in efficiency on both sides of 122 & 126MHz frequency.
Fiberglass antennas have larger transmit bandwidth of 5MHz compared to stainless steel antennas 4MHz as the antenna is covered with a pure copper braid it is a better radiator of energy, It can only work 96 to 100% effectively over 5MHz of the 118 to 136MHz Airband, it is important to tune the antenna to the most used part of the Airband, for example If you tune your fiberglass antenna to 124MHz then it will work from 121.5MHz to 125.5MHZ at 96 to 100% efficiency and then will gradually reduce in efficiency on both sides of 121.5MHz & 125.5MHz frequency.
The ground plane of an antenna, is the metal area (roof) that the antenna is mounted on-top, the dimensions are important and cannot be understated as it is the ground plane that makes a good antenna system. Imagine you are mounting the antenna in the center of a circle, The minimum required diameter of that metal circle ground plane when the antenna is mounted in the center is "Twice the length of the antenna", For example if your antenna is 515mm long then the circle should be a minimum of 1030mm in diameter, So the shorter the antenna the smaller the ground plane needed to be able to tune the antenna to a good SWR. This is why the Airband antenna works so well, It eliminates the need for the ground plane as it is a dipole and has its own ground plane. Please note that ground plane independent antennas are not suitable for Airband, they are narrow banded and are only efficient over a small section of the Air Band.
Antennas mounted on a king post will not tune well, The king post causes the antenna to become a "untuned dipole". You may be able to tune the antenna SWR <1.5:1, you will have a unnatural longer antenna top but this length will be a compromise.
If you are mounting the antenna on a metal airplane then you will have little problems you can use a SW2 or a M124-1 antenna.
If you are mounting the antenna on a fiberglass area then you will need to either create a ground plane by the use of a metal surface such as wire mesh or you will need to use a Mobile One Airkit antenna.
Antennas will not work unless they are mounted on a metal structure e.g. a car, aluminium boat etc, this metal Surface is called a ground plane If there is no ground plane then one has to be simulated! Some ground independent antennas have their own ground plane or have built it simulated ground planes. If you mount an antenna on a fiberglass or wood boat you will need a ground independent antenna these particular antennas do not supply their own ground plane "they simulate them" this is important to note as a ground independent antenna will not perform better than an antenna mounted on its own ground plane such as a metal car or boat. Ground independent antennas have a higher angle radiation pattern and are very narrow banded ( cover only a few channels).
In many marine antenna base section is a coil and capacitor that are tuned to the antenna top, The antenna top is fine tuned to the base. If you damage the antenna top the replacement antenna will not necessarily be perfectly tuned to the existing base, so is important to have the antenna tested with a SWR meter if you replace the antenna top.
Ground independent antennas will work ok on any metal boat
But a non ground independent antenna (monopole antenna) using the boat as a ground plane will work much better