I have tried many different multis and polys in my MGPresMids over the past year and a half.. (all 17g) full klip excellerator, x-1 biphase, recoil, duraflex, LT, gamma prof, weiss canon explosiv, xcel, Kgut,Gosen OG JC and some others. Polys I have tried full-bed (17g) ALU power, optic nerve, pro line II, hurricane, pacific X-force, BBoriginal, topspin cyber blue and BBAce 18g. I have finally settled ( the past month ) on X-1(17g) in the crosses @ 57lbs. and BBAce(18g) in the mains @ 58lbs. I believe this combination fits the MGPresMid perfectly.. since the pattern is so dense and the headsize being a full 90sq.in. Today, I decided to reverse the set-up and keep the same tension. X-1(57lbs.) in the mains and BBAce(58lbs.)in the crosses. Tonight I just hit and played a couple of sets for about 3hours, with this set-up.. just some observations. 1.) I came to this conclusion because I always snap my strings in the crosses, now that the BBAce is in the crosses, durability should be better. 2.) First off the sound was completely different, it still sounded like I was beating someone with a cardboard box.. but this time in the torso instead of the head.. alot deeper, lower more resounding 'THWACK'. 3.) The balance between the multi and the poly was more distinguishable.. when BBAce was in the mains and died.. it didn't matter that the X-1 was still alive and responsive.. as if they had melded together. Now, with X-1 in the mains, the flex of the frame was softer. When the BBAce was in the mains, even after 3hrs. of heavy exchanges it would change sounds, then right before it would die.. it would feel the best right before, it seemed to tighten-up for five minutes, as if it was clinging-on for dear life then die. Not so when reversed. Also, with the X-1 in the crosses, after three hours it would show signs of fray and I knew that I had a limited amount of life left. Even though the dense pattern of MGPresMid does not lend to compulsive string breaking.. it still happens. 4.) Serves were more powerful. The sweetspot seemed bigger and more forgiving with the multi @ 57lbs. in the mains. I didn't notice any decrease in spin production, but definately noticed that the balls were not kicking up high as with BBAce in the mains, the trajectory was lower and fast paced, when they would kick, they would have a more exaggerated spin.. but it was just lower. 5.) Forehands were deeper and the trajectory again was lower with X-1 in the mains.. more pace was noticeable.. but I had to be excessive with my follow through when putting topspin on the ball, almost come up, across my shoulders instead of parallel to the ground, to put some height on my spin. Backhands would tend to sail on me. I have a hard time hitting topspin 2HBH's, it's a 60%-40% battle.. most of the time they are flat and low. Was not a problem when the BBAce was in the mains. Picking up fast-balls early seemed more natural, on both sides and did not feel as if I was running -up hill.. more forgiving and confidence inspiring. With the BBAce in the mains, it was decent but only for a couple of hours of heavy hitting.. after that they would die and the card-board box feeling did not equate to the ease of picking the ball-up on the rise. 6.) Slices and dropshots were $$$$$$$. Seemed as if I was hitting deeper balls with more spin and work with X-1 in the mains. Again low trajectory and a very darting type of spin. With BBAce in the mains the trajectory would be quite higher and more effort was needed to get them deep. Cannot comment on net-play or overheads.. as I spent the majority of the night by the base-line. Overall, I'm happy.. even if the BBAce has started to die.. it is not that noticeable as the X-1's are well alive and show no signs of fraying. After 3hrs. with the old set-up the BBAce would start to die and the X-1's would be fraying. String movement was minimal.. as the BBAce slides back into position fairly easily across the X-1's with little friction. Will keep updating as I move through the weekend and into next week. If anyone has any suggestions or comments.. Please let me know.