Any one use the slack belt attachment on Rob Frinks grinder

[The Zodiac]

Hi
I would like to know if any one has used the slack belt attachment
on the grinder I am also would like hear if anyone has used the hardcore
small on it.I would like to hear how they work.
I have been luke warm about knife making,I sold my grinder and did not
know how much I missed grinding.So for christmas the family is going to get a grinder for me and I am looking hard at robs grinder
He looks like he has made some attachment for it that makes it
real versatile.thanks for any in put.
He is a tooling engineer and is coming up with some good ideas
to make his grinder alot better.