Make sure you raise the lower guide all the way up, and lower the upper guide all the way down.
Since the cut clearance is still going to be about 4", closing up that gap makes cutting a bit easier for knife blade thicknesses. Either cut the slide piece with the upper guide in half and weld an extension on it, or put a slab or two of 2X12 on the table (slot them on the table saw). Lowering the upper guide with an extension is the best thing.
Move the belt and run the saw on the slowest setting.
A clip on tool lamp is really useful when cutting.
Several cool things can be done with the seat.
Go to the local motorcycle shop or someone who works on cycles and ask if they have a junker seat from a scrapped cycle. It doesn't have to be good. Bolt it on the frame.
Get an old saddle that is un-ridable, but still sound. This looks super cool.
Find and old John Deere style or similar backless tractor seat.
Get a "Biker style " seat from a bike shop.
Cut a slab of cypress, redwood, or any wood and make a wooden seat. If you can find an old piece of butcher block counter, that will be great. A Corian cutout from a counter shop will do the same. Check the local counyer shop for cutouts, they often will give you one.
Or, duct tape a piece of 2" foam rubber on it.