Kayak-No go

I tested out my new kayak at Lake Tarpon yesterday. Wow. Not good. I ended up pitching it over about 2 or 3 times before finally getting my "sea legs" and managed to keep it steady. Apparently my fat 195 pound ass was too much for this little kayak to take, and it started flexing right at the seat area- almost as if it was going to fold in half. Crap. This kayak is meant more for kids or for small, petite men or women- certainly not for a dude like me.
So, needless to say, this kayak is not coming along with me on my trip. Although I have access to a much larger yak, and I can easily bring this along with me, I am not sure if I want to go through the trouble now. This other kayak is awesome-a sit in style, about 12' long, stable, and comfortable. But it belongs to someone else, therefore the logistics of security will have me quite worried. After all, I will have to be worried about bike security as well, and I somehow think the two together would be a little stressful.
I'm looking into some rentals now- seems like this may be the better option...