Rather odd you have to trim the whip. The whip on the Predator has quite a bit of adjustment on it.
I've used these antennas and they do work well. They're light weight for it's size and rather long for a shortened mobile antenna especially the single coil version with 27 inch lower mast. This is a good thing because the longer the antenna means less coil matching is needed. This is why it's close in performance to a 102" whip where it won't hardly be noticeable on the receiving radio. It also has good bandwidth so you can run a wide range of channels before re-tuning.
On paper, the 102" whip is still the best due to the fact it's a 1/4 wave at 27 mHz and doesn't need a loading coil like all other shortened mobile antennas. And the bandwidth on a 102 whip is as good as it gets.
Coils on shortened mobile antennas equal losses due to inductive properties required to raise the feedpoint impedance when a mobile antenna is less than a 1/4 wavelength. That's the tradeoff using an antenna with a more manageable height.
However, the 102 whip isn't exactly perfect either, if you check the antenna with an analyzer you should see the feedpoint impedance around 37 ohms, not 50 but it's close enough where it's not going to hurt anything.
When tuning antennas, the CB world says to balance the SWR between channels 1 and 40. All this does is give a compromise tune between those channels.
Myself and many others tune antennas for the lowest SWR at the frequency operated most at and rely on the antennas bandwidth to cover frequencies above and below that point. This is where modern analyzers make doing this much easier by scanning the band so you can see exactly where the lowest SWR is and how much bandwidth it has and adjust the whip accordingly.
Your antenna has plenty of bandwidth, I seem to remember a good +/- 300 kHz between a near flat SWR and up to a 1.9 so there is no need to be concerned as the SWR will climb as you change channels above or below you're lowest tuned point. But, once you get near a 2.0 SWR, it's time to re-tune or use an antenna tuner if you do operate that far away.
Good luck with your setup and mobile safe!
