Ive made the belt too but was very unlucky. Ive tried to put in DET IV into the second slot and the 10th attempt finally succeeded. Guess I dont have to tell you how much gil Ive spent for that slot alone. Actually it was the plan to put in SS IV twice then, but after the first one took like 18 attempts again Ive had enough and decided to use SS III and ACC III for slot 4 & 5. Then I broke my personal record of bad luck and wasted 65 (!) Acc III materias. Luckily Level III materia is cheap but 65?! never been so unlucky before. I bet I will get the dreadwyrm belt today just to rub it in some more.
Ive been thinking bout replacing the materia of my helmet to get rid of 6 acc and swap it for 9 ss but after that belt I better wont touch any materia till a new crafted belt is available.
Sorry to bother you, just had to share this mess.