Having done several conversions now and building from plans not intended for RC I'll give a few of my observations that may prove helpful.
First: You are building a biplane. They are inherently draggy so you are not going to want to go for speed from say a 12x8 prop (1.5:1 ratio). You need gobs of thrust for these WWI era planes so you are more after a prop that has a higher ratio, like 2:1. So a 12x6 prop will be better or better yet a 12x4. I would select your prop FIRST and plan your motor from there. To plan the motor you need to figure out how "scale" you want the plane to fly. I shoot for the lowest possible RPM, which involves lower cell counts and higher Kv motors. My Top Flite Texan is a 60-size ARF similar in size and weight to the Jug in the above video. However, I am only using a 4-cell battery over a 6-cell. The lower voltage allows me to use a slightly higher Kv motor on a larger-than-intended prop for that motor, a 15x10 (fighter and WWII so I need the speed). A good example of this is my O1 Tummelisa. I am using a 16x6 wood prop , which seems HUGE) on a
25 size motor. Knowing this would pull a lot of current I opted for a 60A ESC and a 3-cell battery. While it seems overkill at first, the plane flies exceptionally well at just 1/2 throttle. Any more and it just looks wrong but I have the gusto to get out of trouble. I selected a 4000mAh pack to give ballast (in addition to 8oz. of lead) in the nose... which leads me to my next point.
Second: This plane is short-nose coupled. You will need to build the tail VERY light so that you do not need an excessive amount of ballast at the nose. This is a problem for nearly all WWI era aircraft.
Third: The plans are for Free Flight (FF). These include a lifting tail (airfoiled) that are set at an incidence intended for slow-speed and to maintain a slightly positive attitude. DO NOT be surprised to see your nose go WAY high on maiden. See the maiden of my SE5a.
Fourth: Take-off and landing are ALWAYS fun (knee-knocking). Take-offs are best in the following way: slightly raise the throttle just to get the prop spinning at the minimum RPM. Apply full-back elevator and then quickly advance the throttle to 3/4 or better. Depending on how you power it, be ready on the rudder/aileron to counter any torque the motor will put into the airframe. Your take-off should be short. The very moment you see the plane lift off the ground drastically reduce the elevator and push forward to level out to maintain airspeed. Do not focus on gaining altitude... focus on airspeed. Landing: These are much harder to do well. Reduce throttle to at least 1/3. You WANT the thrust over the tail planes to give authority. make a long approach and ease into the landing and the moment you touch down, avoid the tendency to reduce throttle but apply full-back elevator and let it roll. let the plane slow itself down. NEVER go to full-back throttle until you have stopped rolling. Try to maintain level roll attitude using RUDDER, not aileron. A helpful prayer thrown in sometimes works but do not be surprised if you nose-over--so overbuild the vertical post of your rudder... plan for it to take a beating because of this.
Fifth: The current plan for your motor mount is sound. Typically and IC (internal combustion) plan is more than adequate for an electric setup. The vibration is not an issue and the usual build-ups handle the torque-ups from these motors just fine.
For reference, my electric conversions:
Top Flite AT-6 Texan conversion
Giant P-47 Conversion
SE5a build
O1 Tummelisa
