There Isn't a Stick I've built that hasn't had the firewall chopped and repositioned further back. At least 1/2 of the front between the F1 and F2 removed. Looks better, balances better.
A great many of todays sports models still follow classic RC model designs. Back in those days, engines where smaller, simpler, lighter.
Today we want bigger, heavier more powerful engines, 2 stroke and 4 strokes. The older designs need modification to enable this.
Very simple to establish on a new model before assembly... strap on all the tail feathers, fuselage mounted gear, throw in some servos and pick up the body (no need to attach the wing unless it's significantly swept) and lay the engine, complete with prop.spinner and mount along the front of the fuselage untill you feel it balance. Chop and build a new firewall at the point.