Bike rack and carbon frame question

I have borrowed from a mate the following bike rack to transport 2 carbon framed road bikes to France (pic not of my car and bike, just the type of rack)


The bummer is I am taking the missus' Yaris and couldn’t find a compatible roof mounted system at a lowish price, so I'm left with this Halfords rear high rack and I'm a bit worried about damaging the frames, scratches, blemishes etc. on the long journey and wondered if anyone has had similar with no problems (ensuring the bikes are properly secured obviously ) or has any valuable tips I should consider.

Cheers