OP, is there a particular reason why you decided to go a size up on the more square pallets? because from personal experience, the rectangular ones feel smaller.
The short answer is that the larger grip size brings me back to my comfort level. The complete answer requires some background and explanation.
Growing up, I played Prince racquets with large (4 1/2 & 4 5/8 ) grip sizes. I found tennis again about a year and a half ago after a few years off. Naturally, I decided that I needed some new racquets (toys) and decided to follow the trend (fad?) of smaller grip sizes. After all, if it works for both Federer and Nadal, why not me as well? I gave this a try with 4 3/8 Head Prestige racquets: first MGPP, then YTPMP. The smaller grip size was OK. But, after picking up one of my old Prince TT Warriors with the larger grip size (4 5/8 ), it clicked to me that it was a mistake to follow the smaller grip size trend. The larger grip size allows me to more naturally hold the racquet with a loose grip and not muscle my strokes. This is more so on SW forhands and serves, whereas two handed backhands are not affected. With the larger grip size it is more comfortable/natural for me to take a bigger swing.
The second issue was the grip shape. With the rectangular Head pallet shape, my SW forehand would be erratic on occasion. At times, my grip would drift toward full western while, at other times, eastern. Even when I had the desired SW grip, the angle was not the same as in days gone bye, resulting in a racquet angle that diverged from preference. The end result was a lower racquet angle and thus less spin/margin. On serves, I also observed slightly less spin.
The notion that the rectangular shape makes the grip feel smaller never occurred to me. I have not compared different grip sizes with the rectangular Head pallets. While I could have put heat shrink sleeves on instead of swapping pallets to achieve a larger grip size, this would have increased the weight to a point that I'm not quite good enough to consistently prepare on time with.
I wonder how many others have jumped on the smaller grip size bandwagon, only to realize that it's not for them and return to the familiar and buck the trend also?