Jumper / Leaky
Here are some pics of the modified cradle.
I have also included some pics of the finished model for your perusal shows you what can be achieved with some effort and patience.
The pics should be self explanatory...use a good glue like stabilit express for the steel reinforcement not cheep but excellent, and the size of the Sq rod is so that it is a good fit into the " H " section brace on the bottom of the cradle, use a good grease for the prop shafts, I used Robbe prop shaft grease not cheep but good stuff, I also double bellowed the rear hydroplane and rudder and on / off linkages ( one inside and Out ).
You will note that the tank is at a slight angle this is to allow the piston rod to pass under the central plate when submerging, you will also have to drill two holes into the front bulkheads to allow the rod to pass, I used an engle 825 ml tank and one of his Ballast Tank Switch control boards.
I Use NIMH batteries, a 6v 9ahr pack will sit on the front plate, infront of the rest of the electrics. ( above where the central screw fits into )
Hope its of use.
Regards Sub.