Modern Vespa

I have now completed trips from Cape Cod to Providence, Providence to Newport and back and Providence to Plymouth. Enjoyable rides but I think the seat is affecting how I ride. My shoulders are sore afterwards. The seat is stepped, and I was wondering if it can be changed so I could sit further back.
Are there any OT's reading this that can fix or comment on ergonomics?
Thanks in advance

Bump

Take it or send it to someone who specializes in custom saddle work. Many people on this forum have used Pirate Upholstery with great success. They have lot's of positive feedback.

I have a BV500 which may have the same seat as your 250. The other complaint that I have about this seat is that the drivers portion of the seat is way, too soft. I have a "Butt-Buffer" upholstered, gel pad that I bought over six years ago to use on a motorcycle. It didn't work well on that particular motorcycle so I wound up having a custom seat manufactured. When I bought the BV500, I discovered that I still had the "Butt-Buffer" sitting in a box so I put it on the BV and this time, it helped quite a bit. It raises me slightly in the saddle and offers better padding for the "too-soft" drivers saddle on the BV. I've been using it for about four months and it's helped quite a bit. It's considerably cheaper than buying a custom saddle and it changed my posture enough to the point where I can ride the BV for two to three hours at a time with no problems in my arms, shoulders or butt.