peterm1
Veteran
I have had good luck with adapters mostly. And even with some adapters being smidge too thin, as you say this is only an inconvenience not fatal. Mostly I do not notice it much if at all (if shooting at infinity I tend to shoot stopped down anyway, so the depth of field increase caused by stopping down tends to "cover a multitude of sins".Have fun with the SL.
I'd suggest one of the M to L mount adapters that also has a helicoid in it. Lets you focus closer with M mount lenses.
Ebay had L mount adapters for very little money. Nikon F is about $13 for example. The biggest thing I found when stacking adapters is most adapters are a little too short. So you compound that with multiple adapters. Means infinity won't really be at the stop and the focus scale is off. Both of those are more of an annoyance then anything else. For zooms or lenses with a floating element being too short throws off performance though.
Having said that, in principle I do rather like the idea of buying a helicoid type adapter for the reason you mention. I only have one - that is for Contax to LTM due to some Contax lenses not having their own helicoid. The problem with mine though, is that while in general it is quite well made, the helicoid is a little loose. This makes it a bit clumsy and annoying to use - a certain amount of resistance is needed. for the "haptics" to be just right. I would need to be assured that this does not happen.