Significant? No it only takes a few percent of the hashrate to make a few blocks to successfully Sybil an infrequently connected SPV node, or a full node that h

Significant? No it only takes a few percent of the hashrate to make a few blocks to successfully Sybil an infrequently connected SPV node, or a full node that has been partitioned off for which you have sufficient time to prepare the alternate chain. You're not outracing the network, just making sure the victim doesn't have a view into the real network.