The GOP Establishment is demonstrating that it will engage in ballot fraud to stop Trump. It will not be limited to just delegate allocation. They will try to cheat with primary balloting too.
Trump needs to gear up for a long fight to the end. He needs to arrive with over 1400 delegates to forestall games, and he needs to be prepared for the GOPE to work hand-in-hand with the Dems towards Trump's defeat in November.
There will be hundreds of delegate challenges, going in all directions.
-- he needs to be prepared for the GOPE to work hand-in-hand with the Dems towards Trump's defeat in November. --
Indeed. He will be in the GOP in name only. He is effectively third party, with the GOP and DEM machines (or machine, if you view the parties as two branches of the same company) aligned against him.