Walk and roll!
Adding wheels to a paramotor can make it a whole different craft and there are many flavors. My experience suggests that transitioning to wheels is easy provided the pilot heeds some simple advice as covered in the Powered Paragliding Bible and your qualified instructor.
The variation in craft is dramatic. Additional material will be added to Footflyer under Chapter 6: Trikes and Chapter 28 on choosing a trike. While the term trike suggests 3 wheels, quads are also common which have (as you figured) 4 wheels. Other variations have 5 and 6 wheels. The 8 wheel variant shown at right is too bizarre to name and, to my knowledge, I’m the only one to do it. Inline skating is another pastime of mine so it only made sense to mixed the two. I’ve not seen anyone launch while strapped to a bicycle, either.
The distinction between powered parachutes (PPC’s) and Wheeled powered paragliders can blur. Mostly it depends on the wing. If the same wing is being sold in any quantity to foot launch pilots then it’s safe to say that the combination is more powered paraglider than powered parachute. For review purpose, I classify them in 3 flavors.
1) Wheel Only machines that are not intended to be foot launched. The only difference between these and powered parachutes is the wing. It’s still a wheeled powered paraglider if it uses a wing and riser set commonly flown by foot-launch pilots.
2) Wheel Only PPC hybrids are those requiring special wings or riser sets. The SD PPCg is an example. Although it’s wing is essentially a Prima, it hooks each separate riser set (A’s, B’s, C’s and D’s) to separate connections on the frame.
3) Cart Attachments are, by far, the most common. They attach to a foot-launch paramotor so that it can be launched with wheels.
Probably the most important bit of advice is to never accept a takeoff with the wing oscillating. Every trike crash I’ve seen (and I’ve seen a lot!) has been caused by this malady. It may take great discipline to overcome the urge to launch but it’s well worth it. If the wing is oscillating, either fore/aft or left/right, abort or get it under control first—skip the hospital/repair time and pain.
During launch a trike should lift off the front wheel(s) first lest it try to twist awkwardly. The A’s, if required to be held, should be within easy reach.
If you have good wing handling skills, transitioning to wheels should be pretty easy. In a no-wind condition, wheels make it much easier. In stronger winds, wheels become a liability and require significant skill but can be managed.
There are a many other tidbits, of course, and you’ll benefit greatly from quality instruction.
There are a number of attributes that determine cart characteristics. The most important are wheel base and center of gravity (CG). A wide wheelbase and low CG increase stability.
Some units have a method of self steering where the wing tends to turn the craft in the direction it’s pulling.
Some also have a method to pull the A’s during inflation and others have the manufacturer suggest not pulling the A’s at all although most trike pilots say that is rarely a good idea if the unit doesn’t do it for you.
I’m not an experienced trike pilot but have made 9 flights on 9 different trikes and have yet to blow a launch.
Sport Pilot & Wheels
Wheeled machines do not fall under sport pilot just because they have wheels. As long as they’re single place and weigh less than 254 pounds they’re ultralights and fall under FAR 103 (in the U.S.). If you have another seat then, regardless of weight, it probably falls under sport pilot unless you’re using under a USPPA exemption for teaching.