We're thinking of getting a Dorema Highlander 'drive-away' awning for our Swift Royale 590 MH. According to the Dorema web site there are 2 sizes, Size 1 is for MH's up to 250cm high and size 2 is for up to 275cm high. I'm not sure what size to get, the smaller dimension would come below our existing Omnistor Canopy. Various adverts intimate that the smaller size is for VW Campers etc? I can't find any info on how these marry up to the MH, is there a rail you need to screw on, or does it fit to the groove in the front of the Omnistor 5000 Canopy? Is anyone able to give any advice on these please? Cheers.