Well I just ordered a Profile E- Cavalier from Tom Morris.  I am going to let Tom build the wing.  Tom is recommending a Cobra 2820 for this ship.  I plan to use a KR timer.  I have had good luck with the KR timer.  Battery will be a 4 cell TP.  Anybody that has any words of wisdom on this ship speak up.  Hopefully by next summer I can learn enough of the pattern to go to my first stunt contest.

       

You will probably end up with a motor that will have some 600W power rating.
The trust you need is somewhere around 65-70oz.
Look here and get estimates for power setups for this bird.  http://rcplanes.000webhostapp.com/calc_thrust.htm
I am thinking to go 12.5x7 launch at 6900 rpm. That will use a 364W power and produce 67oz thrust which is great for the application. This estimation seems to be much more efficient than the current low pitch high rpm that produce same speed and thrust at over 400W. You can definitely try it all and see which one you like.  If you look at the prop data chart you can see there that the 12.5x7 seems to be optimum and thus a good start point.
364W per hour is 33.4W per 5.5min flight that is 3000mAh on 3S and 2250mAh on 4S but this is with no head room so ou need to size the batteries some 20% more at minimum to be safe.
840KV ( I am assuming you go with this motor) You can run on 3S if you want.

Put on some build pictures.

Other advice:
Since you go with electric power-plant you do not need the reinforcements the IC motors require. 1/32 and even 1/63 ply doubles are sufficient. The long hard wood motor crutches should be shortened and even cut in half. Holes in the nose are fair game as vibration damping is no longer a concern. Electric compared to IC is slightly heavier but you might be able to recover most of it by taking unnecessary material out of the nose.
You can save a whole lot more weight if you ditch the balsa plank and go with foam core and balsa sheeting for fuselage to make a lighter fuselage.

Traian

You will probably end up with a motor that will have some 600W power rating.
The trust you need is somewhere around 65-70oz.
Look here and get estimates for power setups for this bird.  http://rcplanes.000webhostapp.com/calc_thrust.htm
I am thinking to go 12.5x7 launch at 6900 rpm. That will use a 364W power and produce 67oz thrust which is great for the application. This estimation seems to be much more efficient than the current low pitch high rpm that produce same speed and thrust at over 400W. You can definitely try it all and see which one you like.  If you look at the prop data chart you can see there that the 12.5x7 seems to be optimum and thus a good start point.
364W per hour is 33.4W per 5.5min flight that is 3000mAh on 3S and 2250mAh on 4S but this is with no head room so ou need to size the batteries some 20% more at minimum to be safe.
840KV ( I am assuming you go with this motor) You can run on 3S if you want.

Put on some build pictures.

Other advice:
Since you go with electric power-plant you do not need the reinforcements the IC motors require. 1/32 and even 1/63 ply doubles are sufficient. The long hard wood motor crutches should be shortened and even cut in half. Holes in the nose are fair game as vibration damping is no longer a concern. Electric compared to IC is slightly heavier but you might be able to recover most of it by taking unnecessary material out of the nose.
You can save a whole lot more weight if you ditch the balsa plank and go with foam core and balsa sheeting for fuselage to make a lighter fuselage.

Traian

Traian,

I am looking at a Cobra 2820/12 rated at 530 W max.  The Cobra prop chart does not cover a 12.5x7 prop.  The set up you propose sounds good.  What motor are you basing you recommendation on.  I will be using a KR timer that will allow me to set RPM.
PS what is the source for an 12.5x7 e prop?  EP?