Extreme_RC

I would stay away from the cheap Chinese fans, the rotors are knockoffs and not all that well engineered, they make thrust on the bench but have poor velocity in the air. Also heavy especially the mad thrust fans which are just lander anyway, their 8s fan is almost 200 grams heavier than the Jetfan combos we do, pull more amps and produce less thrust.

Your model is a perfect 90mm size jet, I wouldn't go bigger as you are going to need to clear the deck at the rear of fuse anyway in order to create a scoop area in front of the fan to allow clean flow. I would look at cutting from a little behind the canopy in the shape of the tip of a spoon, like a curved naca duct, around and down to the back where the motor is sitting, then you can create a concave shaped piece that fills this area up, with the fan mounted where the motor is.

I would suggest a fan like THIS as it gives you the best combination of thrust and performance with one of the lowest amp draws for the power. I sell a ton of this 8s version, all the Blackhorse jet fliers go for this as its easy to install, light and powerful, 4.5kg thrust on 8 cells with strong batteries.

You will need to make up a tailcone, tapered down to around 80mm for the Jetfan, around 6 inches long is ok. I would suggest THIS speed controller, its compact and very tough, you can mount it in front of the fan with the heatsink sticking out of the new paneling you install at the back of the fuse. It would all look really neat and work very well. I have had a few customers convert bobcat style models over the years, great performance with the right fan.
If you need any help shoot me an email, [email protected]