You're right in not wanting to cause stress to an autoflower - they don't handle it very well - but LST is perfectly fine and does not faze an auto at all. If you can gently pull the branches out away from the main stem, you can get it to grow almost naturally - in a Christmas tree shape. This might be the best for you so you can get a feel for how it works and will allow those side flowers to get more light and therefore get bigger...
Good luck...