Hey, good job with the express tech. I still use that same soft plate with my tropical rig. In case you didn’t try it, easy to add more grommets to the plate.
Seems crazy that the velcro strap got significantly shorter just with addition of a weight pocket. Are you sure you have the straps threaded same as before on the plate and routed on the buckles the same?
if there’s no way to adjust how it’s threaded, you might consider a STA vs. looping under the webbing on the plate. I’ve long since replaced the zeagle horseshoe bladder with a more streamlined donut bladder and found the STA works better than threading on the express plate. STA for $20 Here:
Scuba Diving Single Tank Adapter Travel Aluminum Alloy Ultralight For Backplate - Walmart.com