show us a pic of the flexis.15mm male couplings would be what i would use as isolators arent flat at the ends like males are.cheaper too.basically cut both pipes,screw the couplings to the flexis,tighten then put the compression side of the couplings onto the copper pipes.you will have to cut the pipes above the top 90'c bends or it will be a pain to get them out of the sink.