The six-year-old was fifth in the prestigious handicap last summer and another appearance on the Knavesmire on August 26 is top of his agenda.
Last year's Northumberland Plate runner-up was strongly fancied to go one better on his return to Newcastle at the start of July, but could finish only 12th of 20 runners.
Seamour was only beaten five lengths, but Ellison feels he was at a disadvantage having not raced closer to the front-runners.
"There was no pace at Newcastle and it turned in to a messy race, it didn't suit him at all," said the Malton handler.
"He needs a proper gallop to run at, whenever he's run well there's always been plenty of pace.
"Also, he was midfield and I'm not sure he enjoyed being around all the other horses.
"The horses that dominated the finish were up there throughout so he had no chance really.
"We'll go to the Ebor now and hope for a strongly-run race."