Yep, you have a problem there. The SL is quite different from the SDL. The SDL has the spring sitting directly on the body.

My only suggestion is to wind the shaft down to make it as small as you possibly can. Then see if you can get it to go into the spring. Once in there, you can get a socket on the shaft and lengthen it .

Those coils look very tight. It's not going to be any fun trying to manipulate the shaft through the plates.

No chance of going through the bottom???