I found the likelihood of the spare wheel cradle bottoming out slim. It happened to me once in 20 years, and that was on a highly illegal looking speed cushion on a Welsh road. If you want to remove it for peace of mind, then you could get one of the excellent see through DIMPA zip bags from IKEA. I have used these for storing my winter wheels on a previous car and the spare for another. This would sit under the bed on a non slip mat with general camping stuff packed around it, or in the car boot if you have space.
Don't forget you are going to need a jack. If space and weight are not an issue then a small trolley jack is best. Otherwise a CORAM, supplied with Land Rover bottle jack is your best option. These are one of the few that will fit under the Eriba axle.

As regards your spare as an alloy, the Hymer/Eriba ordering system will not allow you to order a cheaper steel spare if you have alloys fitted. You spare has to match the wheels fitted. This is basically nuts. I bought a stock/forecourt steel wheeled Eriba with a steel spare. I told them I wanted alloys, so they ordered and fitted two alloys formed and left the steel spare.

Colin

Hi Caravan Nut and others. Can I take this opportunity of mentioning that several new members have recently posted on pages that are blocked from answers apart from members of Administartion.

They are normally headed "Please do not use this board to post questions". In this case your question was posted in UK Eriba Dealers and Clubs so I've moved it for you.
Regards
Randa