"Pat MacKinnon" wrote
I just bought an Icom PW-1 solid state kilowatt amplifier.
On my tower, I have an HF multiband antenna that is rated for 1200W, but
8' above it on the top of the same mast is my triband (2m/70cm/23cm)
vertical.

If the other antenae are directly above your HF vertical you should have no
problems. The radiation pattern is a toroid (donut) shape and antennae
above and below are in the 'hole'. I use a 6m/2m/70cm vertical above a
pair of 40/75m inverted 'Vs' driven by 600 watts and haven't smoked anything
yet. However RF is magic and YMMV.