There is very little difference between the way an Irvine 53 and the saito 72 will fly it IMO. I recently put the 72 on my hard bet (replacing an Irvine 53) and it fly's virtually the same, with possibly even less pullout of hover (color me dissapointed) I am going to try some different prop combinations but then the HB is about 3/4 lb heavier. 3Dreaming has a saito 72 on his sledge and Jeff Williams (designer) said that that was the best flying sledge he had flown so there ya go, flip a coin. I fly the irvine 53 with a tower hobbies muffler and the preformance is outstanding, hovers at 1/3 to half throttle and pullout is great. Jeff likes the MVVS 49 with the minipipe. Pays your money and takes your chances. There all great picks. If you need a 72 email me, chances are Ill be selling it soon and going back to the irvine with a pipe