Absolutely!
I can run 65mm right through the back door on one of mine, and 25mm through another - if I make the needed changes to the set-up. (yank the part ejector cyl mostly)
Now I have another that is NOT set up to doo such thing, but if the rotary union on the back was changed to some other means to actuate the sub collet - then it too could doo it.
Now - with that said - it is not just as simple as having a through holed spindle.
You need to be able to mount up a "sub-spindle liner", and this is much more involved than the one that you have in your main spindle.
You need the liner to be solid and NOT spin with the machine - since you will be stacking parts in there.
This tube will likely be PVC if possible so that it can spin in the sub w/o siezing. (I before E except after S ?)
This tube will stick out the back of your machine about 2' when the sub is HOME.
THEN you need an outter liner that will start at the back of the machine and stick back at least as far as your inner tube, and back as far as needed to get to your discharge point.
Example, on my 65 machine, the inner liner is prolly 6' long and my parts trays set on top of my 1/2 yard chip hopper 2-3 feet beyond the rear sheet metal.
The inner tube cannot fall out of the outter when it is all the way up to the main spindle.
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Think Snow Eh!
Ox