[alanw]

I have no experience with 300# on a yak but in addition to the Hobie PA I might look at the Malibu Stealth 14 (550# capacity), Malibu X-Factor (625# capacity), Ocean Kayak Prowler Big Game (600# capacity). I think Jackson makes a few bigger models with good weight capacity as well. These will be wide (stable) and slowish but you don't want to max out the kayak with you and gear or it might be a wet ride so look at something with plenty of reserve capacity.