In my experience, most FOH engineers willing to let you run mics through the house snake are made more comfortable if you run your mics offline from their system with your own pre-amp/phantom power. If patched out from the direct output of a channel of the SBD, vs. pulling out the snake tails and 'jumping' them to your pre-amp with an extra set of XLRs, all it takes to ruin things is you mistakenly sending phantom back to the SBD. (A lot of SBDs, but not all, are equipped to resist being blown out by having phantom sent back to one of its outputs).