Welcome to the forum. I am also a 2018 Like 200i owner. I am 6'2" and my pants have 32" inseams. Some would say I'm a member of the "chub club."
As a beginner, I've only ridden for two months and 200 miles. During my practice sessions, one of the symptoms I noticed was my knees interfering with the handlebars during turns. On several tighter left turns, I honked the horn with my knees, which would be troublesome at the CA DMV motorcycle road test.
My options were to modify the seat, change my rider position, or quit making tight left turns.
I couldn't see how a seat modification would solve my problem and the road test has tight left turns. So, I changed where I sat on the seat. I slid my butt back until I straddled the ridge (bump, rise, whatchamacallit) and practiced riding from there. For a couple rides, I felt the top box against my back. Then I went to youtube and searched for beginner videos and learned that my weight is constantly shifting in turns and my lean can be into or against a turn depending on speed. It seems my arms (and grip on steering wheel) adjust to my riding position without much notice.
For me, I'm not sure my butt stays in one spot during a ride. So, a seat modification might mean I honk less during left turns, but how is it going to impact my turns? During the CA safety course, I could not have passed from one spot or riding position on the seat. It felt like my body, weight, and lean angle were in a constant state of change. I was never "tucked in" behind the windscreen like cafe racers nor did I scrape my knees on the pavement. I just let the turn, gravity, and instincts tell me where to position my butt on the seat. Plus, it didn't hurt to have a slippery, pleather seat cover beneath me, either.
Now, for my scooter riding purposes (errands, fun runs, no highways, less than 50 mph), this works for me.
But your scooter riding purposes are likely different than mine. If I were in your shoes and still wanted to explore seat modifications, I would go back to the dealer and test every seat on their sales floor, until I found the shape, padding, tilt, texture, width, and comfort that suited me. You'll probably need a tape measure to transpose the numbers between all those bikes and your scooter. Take a lot of pictures and then look for a shop. In San Diego, we have a part of town where all the body, tire, and auto shops are clustered. In the Bay area, I would start in the used car part of town. In there, you might find an auto upholsterer and a decent carne asada burrito. With photographs, they should be able to modify your seat.
Good luck. And have fun.
