I've tried all kinds of things bit can't get my foot to roll in the right angles to heal toe. No way the knee will turn the way I need it to. I've been toying with the idea of replacing the pedals with adjustable Tilton ones.

 

Here is a diagram of how I do it.

 

In my opinion, heel toe shifting is far easier in a mini than in most cars. The first car I practiced on was a honda prelude. The pedals on that car are about 6 inches apart. Ok I'm exaggerating. But they are far nonetheless.
I never measured the distance from the brake to the gas pedal, but they are really close. They're so close that you can do the big toe/little toe thing you guys are talking about, which would be impossible in the prelude. By the way, I loved nabeshin's drawing of the big toe/little toe thing. Especially the diagram of the shoe on the bottom left. Even the piloti rotates with the shoe. Hilariously cute detail.
Like in most older japanese or american cars, the gas pedal doesn't extend all the way to the floor. Some of them have it so that it's not even connected to the floor but is connected up top just like the brake (never understood why some cars are like that). Growing up with german cars, I guess it's a german thing. In the prelude I'd have to pivot the heel of my foot so high that my foot might as well have been perpendicular to the floor. Ok, I'm exagerating again, but you get the idea.
With the mini, I pivot my foot only about 40 degrees and even still the gas pedal hits right above the middle of my foot opposite where the arc is, about an inch below my little toe.
I also like how the gas pedal is depressed about an inch further into the floor than the brake. They line up well under braking. I don't even have to lift my heel to be able to blip the gas. Just brake, pivot without lifting the heel and, like magic, the gas is there in near perfect position about flush with the surface of the brake.
Never had problems with my knees hitting the steering column though. If it where me though I'd probably just lower my seat and move it back an inch to straighten my legs out a bit.
My best advice for someone that is trying to learn would be to practice a lot. It's gets easier as you practice, especially in the mini. It's a bit hard to actually use the heel or anywhere close to it to blib the gas. Try using a place on the side of your foot. I tried to use the heel, but the pedals are just to close. Only then would my knee hit the steering column. And with the gas pedal sitting a bit lower than the brake, I couldn't find anyway place on the surface of the bottom of the gas pedal that didn't feel awkward. There's just not enough room. Try nabeshin's way. Works well in the mini, but if you ever find yourself driving a friends scion or something, your gonna find out that you're gonna have to pivot your foot in order to hit the gas.

Here's some examples. The first one is a tutorial using a mini. Ignore the double clutch part in the beginning. Heel toe part starts at around 7 minutes. The last one is some random race car driver who is pretty darn good.

http://www.youtube.com/watch?v=JcxHi6FlGLo
http://www.youtube.com/watch?v=klMur...eature=related

 

here's what i use.

http://www.srpracing.com/cat_mini.cfm

 

I love the mini's pedals. They are perfectly positioned for me and heal to toe is rather simple. My biggest hurdle was finding the best shoes for it. I have found my kart racing puma shoes (just the nomex puma racing shoe) is my favorite and works the best. Its all about practice, I do it at every stop sign and light. Practice makes perfect.

 

due to the position of my seat and wheel, i cant twist my heel over to the gas so i prefer the big toe little toe method and it is totally possible and even easy in steel toe construction boots. might switch to outmotoring's pedals tho mine are plastic and slippery

 

My Van's lace shoes, are better than my Pilotis

 

I'll let you know after this weekend how those pedals work.