No problem, in a CONVECTION oven, max T° : 60°Celsius* ! (that's the info I was given by my "fitter")
*a higher temperature will damage the boot ! It's like for our skin : at 60°C, it's really hot, but your skin won't burn. At higher temperatures, it will dry, burn, etc. ...
You'd be really careful to lace them properly and NOT walk in them without the guards... BUT don't put the guards too early, because of the T°.
Making it short, you can heat-mold them with the blades attached, but, when possible, it's better without.