P399, if you would like to build a fast little plane with your existing equipment, carve a similar sized wing [to the Cessnas']out of contest grade balsa and build a minimally sized [in cross section]fuselage. Leave off the wing struts and the upper cabin, also make the vertical fin shorter than the Cessnas'. Now you will be all set with a little speedster that will be light enough and tough enough to take pretty much any power source that you can fit within the confines of the firewall.
I build and fly a lot of planes in the 8-11 oz range and have played with various shape and size wings. Try to stay with wing designs that have at least 4 inches of chord and no less than 100sq inches of area for a small speed plane of this weight.
The portions of the wing that you show [above] with the pointed tips would be nothing but dead weight and drag, contributing nothing to lift. Keep in mind that the minimum wing chord for your model is dependent on its' weight, but your model would have to be infinately light to allow that drastic of a taper.