So my issue is whether the weight is going to be too much to get a solid benefit out of the grapple (for moving brush, logs, branches).
I have a Kubota B3300SU as well. I struggled with the same issues.
Here is my setup, which has been very satisfactory for "brush, logs, branches."
I bought a set of ALUMINUM DEBRIS FORKS from Payne's Forks.
These forks weigh only 50 pounds and clamp TIGHTLY onto the bucket without external tools. A little pricey, these were $775 delivered in February 2012.
Aluminum forks do not decrease your lift weight much and are easy to take on and off because of the modest weight. Forks consist of five tines on a crosspiece, the tines stick out from your bucket about 24". I use them for tearing out wild vines up to an inch, just put the tractor in low/4WD and drive slowly into the vines, then lift the bucket/forks and back out. Great for collecting tangled vines and all kinds of "brush" and "branches".
For logs I have two "Kenny's Bolt-On Grab Hooks" bolted onto top of the bucket at the cylinders, which I use with 5/16" Grade 70 chain, with a Grade 70 clevis grab hook on one end and a Grade 70 clevis slip hook on the other. I just move the bucket up to the log, sometimes perpendicular, sometimes on end to lift the log, run a chain underneath, then lock a chain link into each of the two Kenny's Bolt-On Grab Hooks to hold the log to the bucket.....and lift.....up to 750 pounds with the B3300SU. If the log is heavy, over 300 pounds, be sure to have a counterweight in the rear; I keep a Wallenstein BX42 PTO
Chipper on the 3-Pt, which is about 425 pounds. And away to the burn pile.....
I use the slip hook and chain to choke and drag long logs with the tractor drawbar, drawbar is a $49 dealer option on the B3300SU.
This is simpler (KISS) than what you are considering and has worked well for me.
NOTE: Customer Service at Payne's Forks is a trial. Payne's web page is out-of-date, BPayne does not answer e-mails, Payne's Customer Service told me forks would ship in two days and charged my credit card on day of order; forks did not ship for three weeks. Never could get a trucker or tracking number from them. Customer Service from the
Last Century. Good quality product; BAD CUSTOMER SERVICE.
You can Google these suppliers. I also suggest you consider Bucket Solutions as an alternative to Payne's. However, Bucket Solutions does not have aluminum Debris Forks, Bucket Solutions offer Debris Forks in steel.
JBS352