Peter, most of your questions can be answered by visiting
Pete'e astronomy site, he has images etc which show how he set up his LX90, guidescope counterwieght etc, you'l have to hunt around the site a bit but most of the info you need is there. Most people use an ST80 for a guidescope as they're quite lightweight. The weight system is designed in such a way as to not interfere with the forks.