Yes and no... remember, Peco c55 isn't really c55 at all, but c80 that's embedded deeper into the tie structure. There really is no transition between the rails, only between the height of the ties.
The flattened joiner and solder trick is really the only reasonable solution, happily, it works very well.
One other possibility would be to use a length of the Peco c-55 track, and use a dremel to rabit out the bottom of the rail to join to your regular c55. If I remember correctly, the Peco c55 rail actually has two flanges at the bottom, so as long as your cut is clean, you can slip a c-55 joiner right on.
Lee