You really need to just get used to bracing heavy bows, if you want to make them.  Even if your bow is currently 120lb that's a very easy weight to brace with the right technique.  It's still within the limit for bracing without a stringer, as well.  Not the knee method, but the step through works well, as do a few others.
If 120lb is causing these issues, what happens if you want to make a 150lb, or 170lb bow?  Can't use winches and pulleys when you're shooting.  Also, don't worry about winches and ratchets for tillering - they tend to just make it too slow and can sometimes even get stuck.  Set up a good pulley system and tiller the bow with a strong rope.  You can feel what's happening far easier, pull as quick or slowly as you like and it's a much more organic and healthy way of drawing the bow.