hi guys i am just about to install a cambridge roll top bath with a pop up waste but when i done a dry run at fitting it the threads are too short on the pop up to reach the waste pipe beloweven when i take off the top washer ( between bath and pop up ) it only catches by about one or two threads which is not enough can i buy an extended top piece with a longer thread as presently the thread lenght is 20mm with no washers 15mm with washers fitted but acrylic bath is about 12mm thick so not much to tighten