Silver,
That's my bike in the photo. I have had the heel rests for about a year and they have saved the heels on my boots but not the primary cover, which got bent out of shape and started leaking after being scraped a couple times (once trying to keep up with Jimmy 2K through the Smocky Mountain twisties this past May - The dude rides it like he stole it, what can I say).
They make the ride more comfortable since you rest your feet on the pegs/heel rests like you would on floorboards. As far as clearance, well, we are talking about a BO after all!

They don't make the clearance worse than it is, how can they? It can't get any worse (note the primary cover incident above). The heel rests on my bike are set lower than the foot pegs and are the first to hit the ground. So they also help save the foot pegs as I have learned to lift my foot and let the whole thing fold up so I can scrape the primary!

The pegs are $10 each so I will be swapping them out for a fresh pair this winter as the ones on the bike currently have lost a lot of metal around the tip/bottom.
I highly recommend them for ride comfort alone. And as an added bonus the heels on my boots are good as new.
Cam