BigBird,
The dowels are in use all over the country and I have not read one post of a failure. My first one took on a half a dozen pine trees at full throttle and, while the plane lost the battle, the firewall and stand offs were unscathed. We have three of them built the same here and no sign of trouble on any of them. My buddy has his ZDZ 80 in his cap mounted the same way and no problems after 15 gallons.

I used 1/2" spruce triangle and BBQ skewers (bamboo) to pin the firewall.