Don't want to hijack this thread, but ttabbal, how do you like the quality of the Shars parts? I've been thinking about the same setup
for mine.
I've been very happy with the chuck and adapter. You do need to machine the adapter a bit, but it's just to open some space to give you room to adjust and true it up to match your spindle. There were some chips in the threads for the clamping nut, but nothing major. The taper is well machined and accurate, and the threads were easy to clean. I get under 5 tenths runout, and and probably do better now that I have a 1 tenths DTI. Setting it up is just like dialing in a part in a 4 jaw.
Don't sweat the other collet uses, blocks are available for ER, and I bet spindexers and such are available. Even if not, you can hold a collet block in a chuck on a spindexer. Nothing against 5C or other types. I chose ER40 as I like the clamping range and had some good reviews from users here. I spent a little more on Techniks collets as I figured I might use them for tool holding in a future mill and wanted a known good brand that was still reasonably priced. The cheaper ones on ebay and such have been reviewed on various youtube channels and they have been pretty bad. The only cheaper ones I hear good things about are from TPAC Tools.