maybe i am trying to out think myself here.
I know brace height is measured from the string to the center of the riser and the longer that distance is the better it covers flaws in form ect.(more forgiving)
now technically the arrow rest is located very near the center of the riser and in my thinking if you add an overdraw and move the rest closer to the string wouldnt that technically be the same as shooting a bow with a shorter brace height and make for a less forgiving bow,because the arrow rest isnt actually where it is supposed to be (in the center of the riser)

I am asking because my draw lenght is 29.5 inches and i have to use at least a 30.5 inch arrow right now i am using 31" arrows and if i go to an overdraw of 2 to 3 inches i can shorten my arrow length to a 28-29" inch arrow and be able to shoot an arrow that has a lower spine deflection and is lighter. but i dont want to end up with a less forgiving bow.

The short answer is no

By adding a overdraw you are still not changing how long the arrow is on the string which is what makes a bow more forgiving, the longer the arrow is on the string ie short brace the more prone the bow is to hand tourque on the shot.

You should be able to come down to an arrow lenght of around 27.75" with your draw lenght with a standard rest unless you are using a flipper style rest that goes in the burger button hole.

I have a 28" draw and I can go down to a 25.5" arrow if need be.

I'm using a golden key futura rest and it is in the hole of the rest that would bring the rest closest to me.

An overdraw creates a less forgiving bow because it moves the rest farther away from the bows pivot point (throat of the grip). The farther you move the rest rearward the more amplified any movement of the bow becomes as it relates to the arrow.

A short brace height also makes for a less forgiving bow but not in the same way. The shorter the brace height is the longer the power stroke for a given draw length and the longer the arrow stays nocked to the string. The longer the arrow is nocked to the string the more time you have to make movement and mistakes in your shooting.

I have a 30" draw length and shoot a 29" arrow with a trophy taker rest. i could shoot a shorter arrow is I were using a fixed rest like a whisker bisquit.

The better way to shoot a lighter arrow is to go to a different carbon fiber. Pay attention to the grains per inch of shaft length and select one of minimal weight and you'll have the best of both worlds (low arrow weight and forgiving set-up). That being said, with your longer draw length, you already have a speed advantage by your increased power stroke. The increase in draw length should overcome the increase in arrow weight as a relative comparison. In any case, I'd recommend against the overdraw. Shoot the longer, more stable, more forgiving, heavier arrow with more momentum and hit what you're shooting at. Speed doesn't kill, accuracy does.

Looks like the previous responses have covered all angles to this question and I concurr.

looks like the no's have it and i aint gonna go against better judgement.
there are a lot of years experience here that have replied and to go against that would be foolish.
Thanks guys.