Jinma JW-03 Backhoe Info
The following info has been provided by Schmalts, Jay, and Jeff.  JW-03 Backhoe owners and frequent contributers to the CTOA board. 
The hoe is great!  If you don't plan to use it for any really heavy duty digging, it would be fine as is.  But, who the heck is going to do that???  If you do these mods you will have a hoe that BLOWS AWAY any competiters, for less than half the price.   These mods will not take very long, if you have a welder and metal cutter of some kind.   These hoes have a huge bucket and rams, they are too strong for the subframe setup, from the factory.  Even with these issues, I recommend one to anyone looking for a hoe.

1).  Prevent pivot pins from popping out.   The existing middle section pins can pop out when a twisting force is applied.   Get some 1/2" x 1/4" bar stock and weld a piece of it across the open part of the booms, near the pivot pins, in the center section.  (see yellow arrows)  There is one pin that needs it the most.  If you look at the pins, you will see the one that is in the mid-section joint does not go through very far.  It barely protrudes out the other side and does not have a snap ring holding it in, just a S-shaped hook.   I put the little piece of metal across the open area on top of the boom to keep it from spreading, and tacked in the pin, with a few small welds.  If you have to remove the pin latter, a quick pass with a grinder will take of the tack welds.
WARNING: The user takes all responsibility of performing these modifications.
2).  Enlarge outrigger pads.   The small pads that come with the hoe are no good for soft soil and sink easily.  (see circle diagram)  This intern puts stress on the tractor frame.   Weld 4- 5"x 5"x 1/4" plates to the underside corners of each pad.  Eight in all.  If you go to a metal supplier this should cost around $20 to have it sheared to size. 
3). Strengthen lower subframe.  The lower subframe of the hoe will bend if you try to lift the whole tractor off the ground with the hoe.  (see what can happen in picture below)   Weld some square tubing along the bottom of the frame to stiffen it up. 
Note: New JM hoe frames are said to be improved in this area.  Square tubing below the oval cut-out has been added.  Still not as strong as the mod shown here.
4). Stiffen up rear mount.  Make a link that goes to the upper 3pt link.   See picture below.  Great job!  This guy can start his own Implement company!
Rear view of the same lower frame mod.
Some very strong re-enforcing to original hoe frame.