Any small brushless will work fine if it can put out 100 watts or more peak and you could probably fly "sport" with as little as 60 watts.
The wing loading of a typical shock flyer is about 4.5 ounces per sq foot. A Tensor 4D is down to about 3.5 oz/ft. The Capricorn is about 2.5 oz/ft at the lightest.
My latest version weighs around 16-18 ounces all up and I like flying it on a Mikrodan 2505 motor with a 3S TP 1320 pack. It draws about 9 amps for around 100 watts peak with a GWS 9x5 prop. Its more than light enough to fly in the smallest spaces or indoors yet still has plenty of power for wild manovers and water or wet grass takeoffs and is a hoot to fly outdoors in the wind.
The vast majority of each flight is spent well under 1/2 throttle.
I have used motors up 250 watt range with much larger packs. Infact I even flew it in an All Up/Last Down contest with a MikroDan 2510 and 6ea 3S 2100 TP packs in paralell. It still flew fine with the extra weight but wasnt nearly as "floaty"
Jed likes to use much larger motors. He is using Torque motors and running 2100 sized packs. I believe he is averaging more like 200-250 watts peak on his setups.
They are heavier, but a lot faster too. Different styles of flying.
This planform is very forgiving as far as weight and also CG.
I like flying with my CG about 9-10 inches back from the leading edge. I have flown it as far as 15" back but thats a bit much
Jed and most other folks prefer being about 7-8 inches back - right at the rear of the sponsons. Its a lot more stable and tracks better with it forward at that point.
However, if you want to do those super tight loops you need it further back