You are correct - the Single Island trailer is a 200 series.We used to sell it for TI's too, but added the 350 to the catalog to add capacity. They use completely different center beams - so I don't think you can do a conversion - it would basically be an entirely new trailer - your best option would be to trade or sell the 200 version and purchase the 350 - contact Trailex (e mail:
[email protected] ) directly to ask them if there is any way to make the conversion that you're after - but I know those two trailers are very different and think it's probably not possible