Here is info on the HB HDSI Xducer installation with sections for different boat brands...
url=http://www.bbcboards.net/humminbird-sonar-gps/172972-installation-networking-information-resource.html]Installation & Networking Information Resource[/url]

The stock HDSI Xducer can be stuck down in water far enough to get high speed readings but doing so risks the Xducer being damaged by underwater obstacles...

Most glass boat guys are installing a XP 9 20 T thru hull Xducer for high speed 2d readings (using a AS Si DB Y cable) and mounting the HDSI Xducer up higher for protection...(that HDSI Xducer is $270 a pop)...