Please post your SKYLARK trailer model or give more info. Most folks can mount extra batteries on the tongue of their Travel Trailer. The best way was to move the propane tanks as forward as you can and use the wide area between the propane tanks and the front of the travel trailer if that is what you have.
To keep thief down to a minimum alot of folks secure their batteries in one of those diamond plated metal lockable truck tool boxes.
You also don't have to use the provide trays and go on top of them with angle pieces and can even extend out over the tongue area if needed.
This is a typical truck battery install for additional batteries for travel trailers...
sample photo from google images/gilldawg79