You can't convert a 200 to a 350 - the main beams are completely different, it would essentially become a complete new trailer.
Thanks, That was what I was afraid of hearing. Hobie lists the rigged weight of a TI at 195 lbs. so a Trailex with a 200lb capacity puts it an ice chest away from exceeding the limit. Boat will also have weight of the tramps and a Toqueedo motor & battery. Luckily I won't be towing it too far.
I did contact the manufacturer and got this reply from Ken Montgomery:
" I apologies for taking so long to get back with you on this. Right I am working on a couple of new products that’s taking all my time. Get with me the end of February first of March I might have a conversion kit available then for your trailer. If for some reason we get to it sooner I'll contact you. Have a great day!
So, who knows, at least there may be a way. Will update in case others are interested.