When I build my bike rack in the late 90's, I make sure I have all kinds of adjustments so i can carry two very different types of bikes (wheel base vary like crazy depending on the type and obviously the sizeRoad bikes and tall people's MTBs are a bit trickier, as I need to put them in at an angle, and they're not really secured.
one of the features I build was a "Rotating" fork mount (Using snowboard plates for indexing), more than anything to improve clearance lane splitting (California) but never found it necessary..
Same thing you can find fork mounts with rotating mounts so you can lean the bike and keep is solid (I will not recommend this with carbon road bike forks, if you get my drift)
Another tip, alternating the bikes front and back (or up and down like in this case) gives you valuable space because the handlebars don't get in the way..