Amazon Electronic Variation Listing - open to bidding

We need a freelancer to put variations on a listing we have via XML. http://www.amazon.co.uk/Mobile-Heaven-Stylush-Rotating-Function-Protector/dp/B00BI1ZQVS/ref=sr_1_7?ie=UTF8&qid=1384631055&sr=8-7&keywords=kindle+fire+hd+case We need to add different sizes and also different colours. Also it is listed on page 1 of the results "kindle fire hd case" so we do not want to lose the search rankings. If it will affect the search rankings, then we do not want it to be done. We also have a few others where we want to change the title and size/colour however want this one doing first if it can be done. Please advise if this can be done and also what affects the search ranking if anything is changed. Thanks