Transducer question for Furuno FCV600L

[Ed]

I recently bought a Furuno FCV600L and at the time I purchased it, I went with the in-hull puck transducer. Now, the local expert tells me that the in-hull pucks "SUCK" and that I should return it and get the transom mount transducer. He says they suck because the even the best boats have void in the layups (true to some extent, but I am sure I can find a 3inchby3inch spot in my bilge that is solid without any air pockets and is away from the intake for the bait well)which will cause interference and he also said air bubbles caused from the hull slicing through the waves will also cause interference.

I opted to get the in-hull puck for 2 reasons. First, none of my old transom mounted fishfinders never worked above 20mph or so and I like to at least have some sort of depth reading when I am buzzing around. The second reason why I opted for the puck for the Furuno unit, was that I also have a Garmin 188C combo GPS/color sounding unit that came with the transom mount transducer. I just installed the Garmin ducer on teh transom halfway between the engine and the chine. I tried to keep it far enough away from both the engine and the port trimtab. I figured I would keep the Garmin on 50kHz and keep the Furuno on 200kHZ and between the Garmin's transom mount ducer and the Furuno's in hull puck ducer I would always have both fish finding sensitivity and high-speed depth readings.

Does anyone have a Furuno in-hull puck in their boat? What are the pro's & con's of this unit?

By the way, my boat is a 1991 Mako 231. Solid fiberglass hull with a couple of lifting strakes on either side of the keel, trimtabs on teh transom and a 225 Suzuki EFI.