While it is possible to use two motors together, the benefit would be minimal. In fact it is more likely to have the opposite of your desired effect. The two drives would have be in perfect sync, and remain so during the entire session, or there would be a possibility that the two motors would work against each other.
However, you are on the right tracking knowing that the limit of the course size is due to the ability of the motor to move the line/flag at the desired speeds (up to 30 mph).
When it comes to making the course as large as possible, it might be more helpful to think in terms of drag. The motor is quite capable of larger course sizes - and under ideal conditions we have customers who have made courses quite a bit larger than the recommended 200-300 foot courses.
The best way to know the limits of your particular setting is to try it. Set up it, then walk the course. There are two factors to look out for: grass/weeds that are too long; and rises in terrain where the line might be touching. Examine every aspect of the course, tweaking where you can. Strategic placing of the pulleys will keep the line as evenly close to the ground without touching it as possible. If you have dips or hills, placing pulleys at the peaks and valleys will help keep the line an even distance above the ground. It should not touch the ground at any point, nor should it rise too high, as the dog can trip, or get line burns.
Configure of the course to reduce drag as much as possible. The angle of the line at the pulleys is another consideration. Too sharp might put undue drag on the line.
Tension of the line itself is another factor. Too tight, produces unwanted drag. Use the recommended knots to tie the loop and the flag.
Keep trying! Be creative! Keep drag on the line in mind as you practice what works and what doesn't.
Skillful execution of a run takes practice, practice, practice. Keep trying different configurations, trim the grass when needed. Add or take away pulleys as needed.
We also want you to know that we are listening! We are planning a “SwiftPaws Home Plus” version that will allow a larger, faster course. But it won’t be available for a year or two.