Up to you, but I'd never be able to fully trust it. If it's strong enough to bung up hairline gaps between the cylinder head and bottom end, what will it do to the waterways, oilways, thermostat jiggle pin, etc etc? If it bungs those up, you might not know about it for a few hundred or a few thousand miles.
I see what you're saying about using it on a blown engine, but if it *appears* to work and gives up or has blocked some bottom-end oilways and the engine lets go 2000 miles later due to a blocked oilway whilst you're driving somewhere with a camper-load of family and suitcases, I'd lose my sense of humour about it.