I believe I have read somewhere that with a wood stock 35-40in/lbs. is more than enough. Any more than that and you might start to crush the wood.
If you are having problems might be a good idea to put in pillars,you can buy factory pillars or make some from lamp rod,either way it is not that difficult,there are plenty of threads here on the subject but you need to pay for a membership $12 in order to look them up.