BigGuy67 The WheelStop accessory mentioned above is a good solution provided the bike's wheelbase is 46" or less.
How far down does the rear fender come? With my wife's ebike moving the "spool" down a notch or two allows engaging it against the rear tire just below the fender, and the front fender doesn't get in the way of normal usage. We added two
velcro cinch straps for the wheels and her ebike is snug on the rack.
(btw - resurrecting an old thread can lead to people not seeing the date and spending time answering the two+ year old original question before seeing yours.)