The six-year-old was last seen winning the Rabobank Champion Hurdle over two miles at Punchestown in April and his last five runs have been over that trip.
However, Mullins has decided to step back up to two and a half miles for the first time since he was beaten in a French Grade One in June 2008.
The County Carlow handler said: “He is fine. He is well able for the two miles, four furlongs and we are looking forward to Sunday.
“He will be joined by Mourad who is dropping back in trip but should run well.”
Solwhit is the only horse to beat Hurricane Fly since that French defeat and also finished runner-up at Punchestown. The pair clash again tomorrow and trainer Charles Byrnes is confident of a big performance after the six-year-old landed the Morgiana Hurdle on his seasonal bow.
Byrnes said: “Solwhit is in good form. He won over this distance in Aintree on good ground so he should be fine over this trip for Sunday.”
Voler La Vedette was second in the Morgiana and she is the only mare to take up this Grade One challenge.
“Obviously, it is very competitive, but she came out of the Morgiana very well,” said trainer Colm Murphy.
“We would be hopeful of a big run from her in Fairyhouse.”
Mullins, meanwhile, believes Mikael D’Haguenet will take some beating in tomorrow’s Bar One Racing Drinmore Novice Chase.
The six-year-old is making his eagerly-awaited fencing bow after a novice hurdling campaign in 2008-9 which culminated in wins at Cheltenham and Punchestown.
Mikael D’Haguenet missed the whole of the last campaign after suffering a couple of setbacks but Mullins is keeping his fingers crossed for a clean round as he pitches him into Grade One company.
He said: “He is fine — we are sure he will handle the ground OK, we just hope he jumps well. He will be tough to beat if he has a clear round.”
Elsewhere Mullins is unconcerned about dropping Zaidpour back to two miles in the Bar One Racing Royal Bond Novice Hurdle.
The four-year-old, who is a half-brother to 2009 Triumph Hurdle hero Zaynar, made quite an impression on his hurdling bow when coming home 12 lengths clear at Punchestown. Although that victory came over half a mile more, Mullins points to his Flat form as indication that he should be quick enough.
The champion trainer said: “I don’t think the drop to two miles will be any worry. He won over a mile in France and he’s bred to get two and a half miles, which he won over last time.”