hmm if you think cutting the trellis to size will be hard are you sure your up to doing the extension to posts ( no being condescending or at least not meaning to be ) but you have to make sure that it will take the extra load from wind
the suggested cutting method above would be the best and also done best by hand saw if your cutting them with out taking them out first anyway
personally i would suggest finding a friendly carpenter to do it for you
says me lol who has just burnt his hand on the drill putting up my own fence
