Being able to lift the mains up off the ground in a two place gyroplane takes considerable real estate, owing to the weight of the gyro (bigger engine than a single place requires), plus two people on board, a larger cockpit exposure to the oncoming airstream to carry two people SxS, and much larger rotorblades to fly 2-up, w/ more drag than a single place.
Looks great when one views a Sport Copter M-912 doing it in 10'-20', which is also piloted by one of the best gyroplane pilots in the world. Even better is video of the same pilot/machine being able to lift off w/ barely any rolling of the wheels in a breeze!
The M-912 prerotator can bring the rotors up to near flight speed while still on the ground (about 300 rrpms) for a single place machine w/ shorter rotors since it only needs to lift the machine & the pilot.
I haven't seen any video that shows any two place gyroplanes doing anywhere near that, nor heard of anyone having developed a prerotation system that can match that. The exception is when the rotorblades pitch is temporarily reduced & rotors can then be spun up past flight speed b/4 pitch is then restored , enabling the gyroplane to leap off the ground. The Air & Space 18A, Dick Degraw's Gyrhino aircrafts, the Carter Copter, & a few others are examples. They are a quasi-helicopter @ that point, due to their ability to have a collective control.
Usually the best one can expect out of a two place gyroplane is 140-180 rrpms prior to starting the takeoff roll, then build up past 200 & beyond up through flight speed when the rotors can lift the entire machine off the ground.
I believe Wolfy is not as correct regarding airspeed for a two place. 20-30 knots fits a single place gyroplane to starting the lift-off. Any two place gyroplane I've been in usually need much more to levitate. Usually over 50 mph & up, to about 55-65 mph. Larger, heavier rotorblades cannot be rushed into lifting off b/4 they can accept the oncoming airflow necessary for flight. It takes longer to get them up to speed than single-place rotors, which are smaller in disc size & lighter.
A worthwhile project you are embarking on, Supermotive! The drawbacks of the tandem gyroplane solved w/ a SxS cockpit. You're trading the better streamlined cockpit (and lower fuel consumption) that a tandem offers for what a majority of folks want when flying w/ another person, the SxS seating.