I was reading sairose's post, Redfox check and see how busy your SAI chapter is planning the semester. Some chapters do different things. At UK we had several freshmen pledge TBS and SAI at the same time, which as far as I know was never a problem with time and such. But it all depends.....so check with your SAI girls and see! It might be you have way more than enough time to do both, or it could be the opposite!
I'm on the positive end, so I think you can do both. I'm not trying to go against what SAIROSE is saying, but I think you should look into it.