Hummingbird Fishfinder 300C

I am looking for a birthday present and I am pretty sure I am going to go with this model fishfinder.  Usually priced at around $250 I can get it out the door for about $175.  The online reviews make it definitely seem like a solid unit but I want to do some more research before I do so.  Has anyone used this fishfinder on their kayak? 

ALSO: I am considering mounting the transucer in the hull and "shooting" it through the hull.  I realize that I will lose some sensitivity but I am hoping that it will not result in inaccurate depth measurements.  I am mainly getting this unit to get correct depth measurements and look for structure, I would also like to be able to identify my lure in the water if at all possible.  Will mounting the transducer inside the hull significantly impact the performance of my fishfinder in finding depth and structure (and maybe fish but I realize this might be a stretch if I am shooting through the hull)? Water temp is not very important to my btw.  Also, will I have to buy a special type of transducer to be able to go through the hull?

Any advice is greatly appreciated, even if you do not have this same FF.  Thanks!