I've been wearing Specialized brand MTB shoes  basically the entire time I've been on a 'bent, mostly for better walking comfort than road shoes, and for their "wide" fit...  However, whenever I've had a bike with a "hip-level" or higher pedaling position where I have long periods of exertion (Ken's Catrike Road, the Xstream proto, Lynn's hiracer, and my current Xstream), I am developing an irritated and almost blistered area on the backs of my heels -- with the right heel being much worse than the left.  It got really bad during last year's TTTT, making me drop out after only three laps.  
 
I never really experienced this problem on the StratusXP, so I'm thinking it's a result of the more horizontal push-pull of the pedaling position rubbing my heel against the back inside of the shoe.  I had bought new size 46 shoes last week, but after Tuesday night's Pop ride, I was really hurting on the right heel. I took those shoes back to RBM, and got 45.5 from PCF, hoping it would help, but could feel the same thing starting to develop after this morning's Sunday Roll, which was a casual-paced 44 miles.  
 
I've got the top strap ratcheted pretty tight already, although there's some wiggle room in the front due to the width of the shoes. I'm thinking that for my next ride, I'll wear a thin "liner" sock inside my regular sock...
 
Has anybody else riding a hiracer or trike experienced this problem, and if so, what'd you do about it???  Suggestions?  Just putting a band-aid on my heel won't work, due to the sweating, etc...

And I think Sidi generally has a narrower heel than most, which would help if that's the way your foot is shaped.  Some models, like their Dragon, have an adjustable heel cup.  Do you feel your heel slip in and out a lot?

The liner sock idea works well for hiking shoes. You also might try putting a piece of moleskin inside the right heel of the shoe. If none of that works I think the Sidi's are great too.
 
Ken

I have a pair of the wrightsocks and they're quite nice.  You DO wear socks that come far enough up your heels, right?

Dan Driscoll swears by duct tape.

I really like my sandles.  Since they have no heel, there is nothing to rub on.  I suspect the strap gives enough to prevent iritation.  In addition they are cool in the summer and with waterproof socks they are warm in the winter.

I use Sole' inserts.  They are inexpensive, moldable, provide significant arch support.  You put them in the oven briefly, put them in your shoe, step in them and they mold to your foot.  Check out the pictures, especially the heal.
http://www.yoursole.com/products/footbeds/

Quote from barlows on Jul 21^st, 2010, 12:43am:

 
 
+1 for this.
 
Also, look at different socks.  I like the feetures (sp?) Run ON sells these.
 
I've never had any issues with the 'bent other than my feet going to sleep.  I've recently worked through that with simply a better pedaling technique.  
 
I have some some Sidi road shoes and maybe some specialized road shoes you can borrow for a couple of test rides.   Not sure what it'd take to mount the spd cleat on them.    All Size 46.    
 
There are some Sidi Dragon's that are used on Craigs list. Dragon 1(46) and Dragon 2 (in 46.5)  Both are lightly used.     I'd be all over the Dragon 2's if they were smaller, but  I Know the .5 is too much.   I have the Ergo 2 road shoe that I wear.  They were bloody expensive, but well worth every penny.  Probikekit online does a pretty decent job on closeout/clearance.  I think I picked them up for 325 or so shipped.   We're getting close to 2011 product line, so we'll see some clearance soon.