It's highly unlikely that all the pep models you're using for your build were designed with the same scale, so the scale factor will be useless for you. You will have to measure everything, while trying to keep it looking in proportion.
It's up to you if you'd like to share the models you've rearranged, as long as you credit the original modeler and do not claim the model as your own work. To share it, you don't have to have infantryman status, you just have to have an account with a third-party file-sharing site, most here use
www.4shared.com. Of course you will be sharing the models with your scale. Others will likely re-scale the parts anyway, most likely being required to rearrange the pieces again.