A while back there was a poster here that worked for T&B. He made a post about crimping insulated terminals. The proper way is to use a 'Sta-kon' type set of pliers, and use the part of the jaw for uninsulated terminals. One crimp is made on the narrow part of the insulation, squeezing the metal down on the conductor. A second crimp is made on the wider part, squeezing that down on the insulation of the conductor. The second crimp is held down very tight, making a 'cold weld' of the terminal insulation around the conductor insulation to provide strain relief.
I tried that once, now it's the only way I do it. The method works great and actually looks good, too. If I have time later I will make a crimp and take a picture of it and post it here.
I bought a cheap set of metered crimpers from HF and I don't like them.