Hopefully you emptied the tank and still need significant force to lift it back into place. Trying to lift a full tank could a serious issue.
Duck tape or its knock offs do not weather well for long periods. Some recommend Eternabond, but it requires significant pressure to stick. Find a weather proof high strength tape for this job.
A alternative is to put a larger patch piece of chloroplast on and size it so you can attach to frame and cross members with screws and fender washers.
I wish you good luck and happy trails ahead!