On MUI-Prefs MOS, I found no option to set the size.
In Prefs\Env-Archive\MUI, I found a save file named "ASLREQUESTER.1"
I tried deleting "ASLREQUESTER.1" and nothing changed, then I noticed that the file "ASLREQUESTER.1" is automatically recreated if I resize a RequestFile manually with the mouse.
I attach two "ASLREQUESTER.1" files, one is the original one, the other one I renamed was created automatically when I resized a Requestfile.