Some one asked about a router bit for cutting hand holds.
 
Just for a change, try using an angle grinder.  I have a small angle grinder
and a special disk for carving timber.  The disk is made of steel and has
teeth around the edge shaped very much like the teeth on a chain saw.  This
arrangement is very useful for grinding/shaving away bits of waste timber
that you can not get at with ordinary tools.
 
The promotional material that comes with the disc shows that a good operator
can cave some very decorative pieces with this device.  You could use it to
make some very nice hand holds.  I cannot give any practical hints because I
have not needed to make/get any new boxes since I bought the disc.
 
WARNING
If you don't handle them properly, chain saws and angle grinders have a
nasty habit of kicking back at you.
 
I have also used cleats with telescopic lids.  The trick is to place the
cleat lower down so that it does not interfere with the telescopic lid.
 
I prefer to use cleats made for 50mm * 25mm timber and place it at about the
same level where the hand holds are normally cut.  That gives me a
comfortable grip with fingers under the cleat and thumb over the top of the box.
Regards
 
Chris Allen