I can confirm that the recent line of CycloDS's are VERY tight, and do not fit DS Lites properly.
I currently own three, all were purchased from Realhotstuff, two shipped in september 09, both fit fantastically, although I do not use those ones anymore. I recently bought another one, shipped march 30th, and it is tight.. it causes the DSL to "click" when I push it in. it also feels like it is not getting that tiny lift back up when you fully push it down. also to get it out I have to forcibly pull it out(and again it causes the DSL to click) I put it my DSPhat, and DSi, and it fits just fine in both of those