You can try setteng the spring tension to the softest position It's pretty nice on my s200,but I find all the small tire scoots share this problem to some extent. There are after market springs and shocks available.
The seat Is probably the biggest gripe for me on all the kymco's(my only one
) Just think if they had put a yamaha seat on these things. Back in the day we would pop the staples off the seat cover and mod the seats all the time. My sister did this and installed a couple of office gel pads to her people 150 and swears by it. Cut,place and staple back together.