Hey man, here's the key: use a G3-style stock. The CA33E stock attachment is exactly the same, except it's missing the front pin; all you need to do is cut off the front few centimetres of the bottom of the stock. Compare:
to this:
and you'll see exactly what was cut. Quick and easy with a dremel. Also, I found that the stock was EXTREMELY tight on the body, so I sanded down the inside of the stock attachment a bit. Thankfully this makes the whole gun ROCK solid, more solid than with the "solid" stock.