I am considering enlarging my pond and I have a main concern regarding the liner. Right now my pond is 8x6x2.5ft. (or 240x180x80 cms roughly) My liner is already 15x12ft (5x4 meters) but I'd like to increase my pond to 15x10x4ft (500x350x120cms) or close to this measures. I'd like to use the old liner and buy some new one to make it up to the size i want to increase the pond. Would be a good or safe idea to glue the liner together? Has anyone tried to (successfully) glue two bits of liner before. If anyone has any idea please advise. Also if someone have used any brand of glue that would recommend it I would be glad to hear some advise.

Thank you in advance
Eddy