Martin,
I am glad I only read about the tight tolerances AFTER re-doing my RL140s. I would have perhaps not attempted it!
Having started with a pair of CX100s I moved on to the speaker in my LX2500 (no direct replacement listed but a close match found) and then tackled my RL140s. I found that lots and lots of clothes pegs to help keep it all in postion were helpful. On a small speaker 4 - 8 would do the trick, but on the RL140s I think I used about 16!
I would also recommend taking a picture (or 2) of the inside of the RL140 when taking it apart just to ensure you put the interior back the way it was. WIth 4 woofers to replace it was almost a week to do the job for me and I was gald of an image to help relocate everything.
Brian