Raspberry Wheat + High Mash Temp = Sweeter Fruit Flavor?

I searched and searched and could not find any info on this.

My thinking is that if I use a higher mash temp (156?) on a wheat/rye beer there will be more unfermentable sugars that will aid in bringing out the flavor of the raspberries.

If you are familiar with McMenamins Ruby ale then what I am trying to avoid is the weak raspberry flavor and try to have a beer that both tastes like beer and has nice sweet-ish raspberry undertones.

Being a bit of a purist I'd like to avoid using fruit extracts, acid blends, and lactose. Of course if that's the only way then I'm open to it!

I think you'd still want to end up with an easy drinking beer which requires it to dry out a bit. However, you probably want to address the perception of sweetness by backing off on the IBUs quite a bit. I'm shooting for 8 IBU on an upcoming strawberry wheat.

I think that as long as you're using real fruit this will help out a decent bit with the issue that Bobby_M brings up. Most all of the sugars in the fruit will ferment out and this should dry the beer out some. Remember though that a lot of what is left as unfermentable when you mash high isn't sweetness but instead is malto-dextrins that contribute mouthfeel more than actual sweetness.