Slingbacks from Hell

I am wearing these shoes- yes, the ones pictured here, but in light brown- and I love the way they look but can't stand the way they feel. Below is my tragic tale of woe.

I bought them years ago at Macy's, and wore them to work periodically. They are a lovely shoe for spring and summer, and look great with pants, skirts and dresses. This morning, I scoured my closet for the perfect shoe for my awesome brown striped anthro trousers and it hit me- the Guess Rally peep toe sandal! Neutral but fun, and high enough so my hem won't drag on the ground. I strapped them on and was out the door.

Sadly, upon walking on any surface other than carpet, my feet slip, the slingback slides down, and I am generally a wobbly mess. Not cute, people, not cute.

I buckled the strap tighter. Now it hurts and it's STILL slipping. WTF?!

I haven't even gotten to the part where my hems are getting all bunched up under my heel.

I have heard tell that a shoe repair shop can shorten the strap or add extra holes for the buckle. But does it really work? I have even seen apparent solutions to the pants bunching issue: Kix by Katie (http://www.kixbykatie.com/) is the most convincing one I've seen so far. But is it worth it?

Also, I saw these Strappy Strips from Foot Petals (http://www.footpetals.com/cgi-bin/footpetals/Strappy%20Strips.html)- do these look promising?

A friend and fellow shoe lover has tons of slingbacks and loves them. Does she have a bumpy heel?

Ladies, I beseech you: How the HELL to do you wear slingbacks?!