Fairing the nose in on an e-bird like was done on the Vagabond build is a nice thing to do and would improve the looks of the Kaos significantly. However, using a thick 1/4" ply former up front as shown in your picture, makes life harder. You now have to fair a 1/4" piece of square ply into a circular spinner sized diameter. Not something I'd want to do. If anything, you're better off cutting a 1/4" disk the size of the spinner and mounting the motor directly to it through the front. Like you have done but not on a rectangular piece of wood.

It is considerably easier if you use a piece of 1/4" or 3/8" rectangular balsa sandwiched in between the "cowl cheeks" up front. You align it so that the hole you'll make in it will be centered on the thrust line. You then take a piece of 1/16" ply and make a ring - probably 2" or 2-1/4" outer diameter for the Kaos as this is a good sized spinner on 40's. Carve out the inside of the balsa backing from the ring opening in the ply and you have your thrust washer (prop adapter) passing hole. Behind the balsa backing "former" you add 1/2" or 3/4" tristock in the corners going back to the original firewall. Add a sheet balsa bottom and you can then carve and sand the nose to contour fairing it in with the FW in the back and the nose ring in the front. The 1/16" ply ring makes the front stiff, provides a carving guide and the whole mess is much easier to shape and sand than producing a circle out of a rectangular piece of 1/4" ply.

I've attached a drawing showing the 1/4" balsa former and rings that I've made to produce the nose of a model I'm currently designing. The 1/16" ply ring with the smaller hole is to be used as a spacer. You mount it on your engine/motor, add the spinner backplate, lock it down and then you can see exactly where the motor X-mount (or engine mount) winds up. Measure the distance from the back of the X-mount to the firewall, cut standoffs that length (as the Vagabond builder did) and mount your X-mount by passing screws through the standoffs into blind nuts in the firewall. The former on the bottom is the e-firewall. One can see the offset mounting location for the motor (right and down thrust) as well as a hole centered on the motor behind it. This removes some weight and allows airflow. The hole to the left is to pass the motor leads to the ESC behind the FW. The hole on the bottom are the main cooling passages - plenty of air over the ESC and battery which is also cooled from above over the FW (not the case with a flat top design like the Kaos). The spinner rings are 1-3/4" diameter in this case but the concept can be used for any size model with a contoured nose.

You can often place the ESC on the standoffs under the motor, or, install it on the underside of a battery plate in the tank compartment. The ESC goes underneath and the battery on top accessible through a hatch. You can make holes in the plate to lighten it and you can also make at least two holes in the FW, one behind the X-mount to allow a driver access to the motor screws from behind and another to pass the leads into the tank bay if you position your ESC there. If you are running your ESC at 50% capacity or thereabouts, it will barely need cooling. You can add other holes in the FW making sure you don't weaken it in the X-mount standoff areas to allow more airflow over the battery behind it.

I understand that logic but in the case of classics where we want to turn smaller propellers at higher rpm, the opposite equation is preferable (while it may not be preferable electrically) - drop the voltage (5s or even 4s can be used) and up the capacity - the weight can be made equal to a 6s setup. Keep the Kv high and the prop will spool up to higher rpm with lower voltage. So long as you use a good ESC capable of the current draw of 40A - 50A and a little more (i.e., 60A ESC) and provide sufficient airflow, there is no issue.

Just some ideas for "Mark II". [8D]

David