My tip would be not to try to pick a Grand National winner.
Instead, spread your bet and back several each way at the 16/1 to 20/1 mark, FIND A BOOKIE WHO'S PAYING AT LEAST FIVE PLACES and for good measure, hope that they may also be doing a grand national matched bet or something.
Bet365 are already offering 5 places plus if your selection is a non runner you get your dosh back.
Very early thoughts...
L'ami 20/1
Knowhere 25/1
Phillson Run 20/1
Possibly Joe's Edge (although I'm pretty sure horses that have run at the Cheltenham Festival have a poor record this soon afterwards at this race.)