Yes, I would make changes. Originally, the rack was for 4 29g aquariums at 12W x 18.75H. The 55g is 13W x 23.5H leaving only 3 inches of access. When I aquascaped the 55 I had to remove the 2 29g from the top.
As built each “shelf” should be able to hold 600lbs (see weight calculator link above). 2 29g are roughly that weight sans decorations so they should stay bare tanks. The 55g is roughly the same weight hence the center brace. Future build would be 2x6 long cross members for more weight bearing.
So, I would lower the 55g by 6in to allow more access. I would add additional storage shelves above top tank and raise upper cross member a couple inches.
If I build another rack for 29g I will add a 1/2in to total width. 2 29g side by side are 60in and between uprights is 60 3/8in. Made the sides really to close. I would also turn the uprights 90 degrees so that they are parallel to long cross members so side view of tanks is not blocked as much.
Cory built a rack out of metal bed frames. I am currently collecting same for same.