The unit you listed does Side Imaging and is a bit larger than the regular 2d sonar ducers. For best side imaging performance the cone angle should not be blocked by anything. Having it in the pocket may cause some hull interference and it might not fit without cutting a hole in the pocket plastic cover. Your yak is plastic so it may not be much interference, but some prefer to mount the SI ducers elsewhere to avoid any issues with interference. I have the Lowrance SI ducer and it is way to long to even fit in that pocket area. Your HB compact SI ducer might fit with some modifications. Check out this older thread - same deal:
viewtopic.php?f=78&t=46839