I don't do that, but I'm confident that it can be done. As long as the powder is completely dissolved, you should have no problem. Just remember that you'll have an extra-concentrated stock solution which will need more than the usual amount of water to make the working strength of your choice. XTOL is an excellent developer, and I think you'll like it.
I would also like to caution you against these collapsible containers. I have a couple of them sitting around too, and find them to be next to useless. They don't seal well, are made of the wrong kind of plastic, HDPE, and are unstable when full. PETE plastics, the kind soda pop bottles are made from, are much better for this application. I've been using recycled soda bottles for years and have not been let down by them.