Our ~3 minutes or less GT loading procedure:
21' Featherlite with e-track spaced for GT and winch offset to driver's side and complete w/remote. Winch cable stored in "out" position and typically clipped to one of Featherlite OEM rear-most rings. 3500lb axles on Featherlite (ride height almost 3.5" lower than same trailer with 4500lb axles.)
1. Parking brake on tow vehicle. Air suspension in "up" position to induce slight trailer angle. Trailer side door open; Rear ramp down and 12" transition ramp flopped over. No need for ramps, wood, etc. even with very lowered GTs.
2. Drive GT to ramp and more or less centered. (Not that critical.) Parking brake on. Connect Cool Tech tow strap to OEM boss at front of GT. Use winch remote to remove line slack.
3. GT parking brake off, car in neutral, key in first position (unlocks steering wheel), driver's window down.
4. Remote winch GT into trailer. Make slight steering adjustments if necessary. Walk anywhere around GT to insure clearance/straightness. Winch until front right tire (at trailer door) reaches clevis of over-tire strap.
5. Secure front right strap over tire and cinch down.
6. Release 3-4" of winch tension.
7. Turn key off and remove from ignition and set parking brake
8. Secure remaining 3 over-tire straps
9. Close trailer doors.
Having done this a hundred or more times, we have it perfected and can have a car fully loaded and secured in about 3 minutes. I would NEVER opt to drive a GT into a trailer where, by comparison, I have very limited visibility when compared to my full roaming around with remote winch control in hand.
LOVE the looks and the quality of the trailer you purchased and agree that large side door provides great access to the car which is very restricted otherwise. As for loading/un-loading, I would choose to do by winch regardless of the trailer set-up.