Two things about extending the arm on a cherry picker lift.

As Maddog points out, you need to extend the front wheels to where they further forward than the lift hook. If the hook is forward of the front wheels, the rear wheels will lift. If the hook and front wheels are in the same spot fore/aft, there's no weight on the rear wheels except half the weight of the cherry picker itself. As you move them further forward, more weight will be on the rear wheels.

The other issue is when you extend the lift arm, you reduce the capacity of the jack to lift a load. Let's say the jack could pick up 1000 pounds with the arm that's on it. If you doubled the arm length, you could only pick up 500 pounds.

The way I pick mine up is to use the cherry picker on the rear of the body. I have a brace I put under the trunk floor where the rear gas tank bolts were, and screw two eyebolts through those bolt holes. Then use a chain between them and pick up on the chain with the cherry picker. No need for extensions or anything to the cherry picker. On the front I put a sling through the cowl braces and lift with a comealong from the ceiling. Obviously where you attach to the ceiling needs to be strong enough to accept the load.

There are lots of ways to adapt things using what you have and things that suit your shop's (or lack of it) layout. That's why Nick correctly points out that he probably can't sell too many of these because everyone's needs and idea of how to do it will vary.