Maitreya Lara Pants Not Rigging Properly [Second Life]

Hi, I have some pants I need to rig to a Maitreya Lara Body

They rig fine in pose, until the body moves and then there are problems with the seems and in general the material doesn’t stretch and there are gaps and spaces

If you know how to fix this or are able to take a look it would be kindly appreciated, or if I can suggest a design similar to what I have attached and you can do it that would work too