What's with "Mr Tuffy"

[KnowWhen2HoldemKnowWhen2Foldem]

I've used Mr Tuffy for 7 years on my old mavic road rims. Never had a
problem with a flat caused by the overlap area.

I recently bought a new bike. Ultegra WH-600 radial wheels. Since getting
this bike I have ridden about 650 miles. I have had no rear flats with Mr.
Tuffy. The front wheel has had repetitive flats from the place where Mr.
Tuffy overlaps.

Is there a way to install Mr Tuffy to minimize this problem? I tried
tapering the rounded edge by reducing the thinkness of Mr. Tuffy where the
overlap edge occurs. This was done with a scissors cutting the thickness of
Mr. Tuffy on the hard shell side so that it more smoothly transitions from
the top piece to the bottom part which is overlapped. I also taped the
overlap with electricians tape. I still got a flat from the overlap area
at 500 miles.

This just seems strange. I examined Mr. Tuffy and it does not look like
there are any observable problems. I did wonder whether the overlap should
be facing away from the direction of the tire rotation but I decided to ask
here before doing anything to the current setup. (The reason for facing Mr
Tuffy away from the tire rotation would be to minimize the rubbing friction
the tube might encounter when the tire contacts the road surface.)

 

[flatline]

I used to get flats at the overlap where the Mr Tuffy edge hits the
tube, but I got over that by covering the edge with duct tape and
reducing tire pressure to 100 psi.
I also trimmed back the overlap from about six inches to about two,
which the instructions warn against, but I see no discernable effects.
I don't worry about the direction of tire rotation.
I use Mr Tuffy only on the rear wheel. Tires are 700 x 23c and I weigh
a little on the heavy side at 190 lb. Flats are rare for me on both
wheels.