I have a 2015 Ducato chassis (not Alko) on my Burstner and no spare wheel. I'd like to fit a spare wheel carrier and note a lot of holes under the chassis where one was likely fitted. But these have no captive nuts. I'm assuming the latest Fiat spare wheel carrier will fit but what do I need as "nuts" for the fixing bolts to screw into? Has anyone actully done this. I see several posts from people asking the same question but no results.