1/55 perfect method to separate the thruster shell from the tail plate

[GrampaStump]

Often the thruster shell is glued to the tail plate.  Sometimes it cracks loose easily, other times it doesn't.  I have more than one that someone else broke trying to disassemble.  Has anyone perfected a method for separating them?

 

I have soaked the seam in goo gone, reapplying every once in a while for a day or two, and then used a very sharp razor blade to get them apart.  I've also managed it without any tools, just being a little forceful with it, but that seemed awfully risky.  I haven't done it enough times to really get a sense for whether the goo gone actually helped.

 

It isn't easy, any way you slice it (pun always intended).  Very easy to cut into the plastic with the razor, or break the shell if you rush it.  If the goo gone actually works, I'm thinking that the best way to do it would be to build a little jig to put the whole assembly into, soak it with goo gone for longer than I have ever done it (patience!), then tap it apart with a soft mallet - no knife involved.

 

Am I reinventing the wheel?  Has someone out there already perfected this?

Also, secondary question, is there rhyme or reason to which ones are glued and which ones are not?  Possibly early ones / Takatoku had no glue, but Bandai do?  Not sure...