You can use this longer wheel strap in place of the standard frame strap. This strap doesn't clip into the holder as it has different end on it, but it still tensions up correctly. Because it doesn't clip into the frame holder, you'll need to either remove it when not in use, or feed the strap into the ratchet, otherwise it may fall out.
Alternatively, some people just like to use a longer fabric strap and use this to secure the bike to the frame holder, wrapping it through the cradle and around the tube of the upright. Something like the Fasty 50cm strap usually works well.
This photo shows a webbing strap used with a similar rack, but it should give you some idea: