Great job on the sonar case. Just be careful using any sonar for ice fishing application. I had a trusty 320 fishmark and used it for years on the ice until one very cold blistery day the screen blacked out. I contacted Lowrance and they advised me that not all LCD screens are meant to be used in extreme cold. Needless to say I was SOL as far as warranty.
I picked up an X67 ice machine , should be good for icefishing I thought and It has been great for the last several years. ( I really don't think that there is anything magical with this screen ).
I picked up this one without a case/bag so I made one from one of those lunchbox coolers, just the right size and it's orange which makes it easy to see on the ice and hopefully won't get forgotten when packed up to leave.
I mounted the gimbal bracket on the inside of the flip up lid and with the head disconnected it fits nicely for storage with everything including the 12 gel cell battery.