I've ran into similar issues that when a project gets significantly large enough (usually 100MB or larger), that ReadyAPI takes awhile to open it. One way I've been able to get around this is to ensure that your memory settings in ReadyAPI are set large enough to handle said project. You can see a guide for adjusting memory settings here.
I've allowed ReadyAPI to use a lot more memory which has helped me open 100-200MB project xml files.
The file size of my xml file is 623MB. I tried to increase the amount of allocated memory (increasing the -Xmx on the .vmoptions file) but that did not work. I was still unable to import the project. My work PC has 8GB of RAM so the recommend value by SmartBear is half of that (-Xmx4000m). Would allocating more memory resolve this issue? Feels like I would need about 32GB of RAM (-Xmx16000m) in order to import this project if that's the case.
The largest I've gotten a project is ~200MB, and that took 2-5 minutes to open on my machine. I have 32GB of RAM and set my vmoptions to 24GB.
