I'm not pretending to be an expert, but have just done the same with my HDS-5. Here's what I found from my research:
Make sure the transducer is level. Either attach to a stick and attach stick to bucket or use pipe insulation foam and cable ties to get it to float right. Make sure to fuse the positive side of the power cable coming from the battery. If your ff has the option, turn up the scroll speed. You'll need to play with the sensitivity/gain/ping speed to dial it in just right.
I set mine in a tackle bag that normally holds 4 plano boxes. With the existing RAM mount, I can adjust the way it angles quite a bit and still use the lid of the bag to shade the screen. Had the batteries already from my duck decoys. For the transducer, I used putty knives, cable ties and a bolt. Hope to try it out as soon as the ice gets thicker.
I know that there's a lot of flasher die hards out there, and likely for good reason. But for <$10, I converted my graph and that's enough for this amateur.
Here's a pic another guy had of his xducer:
My cable came out the other side, the putty knives are bolted on either side of the hinge point and the bolt torqued really tight. Then I adjusted the angle of the blades so when the cable was sandwiched between the blades, it would be above the center of gravity. Cable tied the blades together and then duct taped it all b/c you can never have enough duct tape!