ghostrider_tlr 1st welcome to the site. 2nd No the seat height can't be adjusted. If you need to get closer to the ground several seat manufactures make what is known as a low boy seat. There is also a product made called Tallman shoes which in effect is a platform that some of the guys here like. I'm not sure why you ask but if you are more specific I'm sure one of us will have an answer for you.
Welcome to the forum from the Keystone state. Fossil is right, there is no adjustment on the GL1500 or the GL1800. I had a Saddleman Road Sofa seat on my 98 GL1500 which was set for a 29" inseam. That worked for me. You may be able to find a local upholstery shop that can cut some of the foam from the seat. Good luck..