As long as the bolt pattern, width, and MOST importantly-The OFFSET is the same. Then Absolutely. CSC is somewhat more forgiving than others in that there is more leeway with the offset toward the outsides than most kits. Their GL1800 kits have more "space" between the outside surface of the stock tire/wheel combo and the inside of the fender wells. This will allow you to either go outward with the offset more or keep the same offset but increase your width of the tire/wheel without causing a rub. Obviously most subscribe to the "Wider is Better" when it comes to tires for contact patch, handling, braking, etc...
However, keep in mind that a wider tire also has a negative/con/down-side in that it will magnify the grab of the road surface and be more effected by the same (the contouring and imperfections in the road surface will transfer more readily and noticeably into the trike). When this happens it will cause the rear to want to "wander" more in side-to-side motion as you are moving forward. Not too big a deal once your brain gets used to the increased sensory input you will experience as that "wandering" goes from road, throughout the trike, and into your body.
Also remember that by decreasing the rim diameter, you must increase the tire wall height to retain the same overall diameter of the combination. The taller the sidewall-the more lateral Yaw (due to increased sidewall flex) you will feel in cornering which can effect your riding style and set-ups into those. You don't "have to" do this but if you don't it will bring about its own consequences that may or may not be a negative to you individually. Such as: 1. Speedo will read inaccurately (can be correted with a Healer). 2. The powertrain will have to turn more RPMs to maintain the same speeds as before. 3. Your operating ranges of the gearing will change (more noticeable on the first 3 gears).
Number 1 isn't much of a deal at all but numbers 2 & 3 can be over time. Increased RPMs and working of the powertrain can lead to abnormal wear and tear on those assemblies as they are constantly performing above and beyond its original intended design. You will also experience a decrease in MPGs and the tires themselves will wear faster due to increased revolutions and heat and friction. Brakes and rotors will be affected in a similar fashion.
I know it sounds like overkill and overthinking but it is true. Ya gotta think through the whole picture as the Tires/Wheels are a big piece of the overall Unit and machine. Any seemingly small and negligible modification to any machine can translate into a big change for the whole when set in motion. As the Law of "Every Action has an Equal and Opposite reaction" also applies, there is usually a Con/Anti for every Pro/Positive. You just have to smartly and thoroughly weigh them both and decide which "Pro(s)" you want more and which "Con(s)" you are prepared to have to live with. Then pull the trigger and rock-n-roll.