Tortuga.. I have followed the Fink plan, for an IronMan, and found it very good... mainly the intermediate one.
The reason I will try to keep my HR low on the bike after including tempo runs in my schedule is that my focus is running until Spring, and I know through experience that a hard session on the bike leaves me empty for a couple of days.
If you're planning to do an IronMan (next year ?), then building a big base by following HADD and doing low intensity cycling/swimming before starting the Fink plan starts would be an excellent idea.
As for your HR problems.... I'd be surprised if 180 was your max, you'll need to work it out.... go blast some hills on the bike till you feel like vomiting... that'll be your max. Also, don't worry about finding it difficult at first to keep the HR low... it is.... perservere and you'll get there.
Edited: 21/07/2012 at 08:59