Thanks for all the good advice on my power budget and alternator sizing.  It will take a little while to digest it all, but I still have a few weeks before I need to walk over to Bill Bainbridge's booth at Oshkosh and buy an alternator.

For Shannon -- no, I was going to use the antediluvian vacuum pump approach.  This saves me about $2000 on gyros ($500 vacuum gyros vs $1500 electric gyros) and eliminates the complexity and cost of a dual electrical system (whose extra cost is probably comparable to a vacuum pump system).  Since my IFR plans are rather limited, and there are now vacuum pumps whose vane wear you can measure, and I plan to have a low vacuum warning on my Jim Frantz annunciator system, I think the risks of a potential vacuum failure are small in my case (note to all -- your case may be different).  I certainly understand why folks choose all-electric, and have no problems with this approach, but I'm choosing not to do it.  - Rob Wolf