O'Neill sees the nine-year-old, who was sixth in the Cheltenham Gold Cup, as an ideal type for a race he won in 2010 with Don't Push It.
By contrast, the trainer has withdrawn ante-post favourite Minella Rocco, who was a fine second in the Gold Cup but will not run again this season.
O'Neill said: "Minella Rocco ran a cracking race in the Gold Cup, but he had a hard race.
"He's only seven, so we've decided to take our time with him and give him a rest and bring him back next season for another go at the Gold Cup, and then maybe the National.
"More Of That ran a good race at Cheltenham and we were happy with him in the Gold Cup.
"We've another couple of weeks to go and we're hoping to be here (Aintree).
"He seems perfectly fine at home so it's full speed ahead (for the National).
"You need all the luck in running in the National but he seems in great form and if he sharpens up in the next week or two we'll be delighted with ourselves.
"He's not as fast as he used to be so he's the right sort of horse to come to the National with."
O'Neill has also withdrawn the 2014 Irish Grand National winner Shutthefrontdoor, who will instead return to Fairyhouse on Easter Monday.