40% Loss of Downscan on Lawrence Elite 4 HDI

I am installing an Elite 4 HDI unit on my Trident 13. I called Lowrance Tech Support about a transducer issue.  He said that going "Thru Hull" would degrade the downscan performance by 40%.  Has anyone noticed this on theirs, and how bad is it? I don't see how I could put the transducer under the kayak and land on a beach.

I would say there is a degradation in sonar quality but maybe not 40%. (Or from what i've noticed). I have done thru the hull and directly into water (hobie 2015 model), and the quality is marginal. You won't miss a bait ball if it floats under you. Maybe others have a different experience. Hope this helps.

http://www.kayakfishingmagazine.net/articles/139-kayak-fishing-how-to-articles/1822-down-scan-imaging-down-imaging-shoot-through-demystified.html

 Told that the Hook 3 experiences higher losses in a shoot thru because it is a low RMS wattage unit compared tp the 4/5/7 units.  I would not suggest a shoot thru for the 3 if loss is a concern.  Other than that, I've heard no losses in the percentage rate you mentioned.  Any loss experienced will be uniform across all manufacturers, not just Lowrance.  The higher the frequency I would suspect the higher the loss.  The DownScan operates on 455/800 with Lowrance so I'd assume the loss to be higher on the 800 than the 455 frequency.