the problem is that as you get to the bottom corners, the chain to the near
motor gets close to vertical. That means that gravity doesn’t provide much side
force to swing the sled into the corner. A wider top beam means the chains are
not as close to vertical in the bottom corners.
as you get to the top center, the chains get closer to horizontal, which means
they have to pull really hard against each other to move the sled up. This
either runs out of motor power or wears the gears out sooner. moving the top
beam higher means the chains are not as close to horizontal in the top center.
making it wider hurts the top center (but not as much as it helps the bottom
making it taller hurts the bottom corners (but not as much as it helps the top
so going both higher and wider than stock helps both 
this spreadsheet lets you play around with dimenstions to see how what you are
looking at compares to stock (including allowing you to define different
as for angle, we know that it doesn’t work at 20 degrees. we know it doesn’t
work at 5 degrees, 15 degrees was the stock design and we haven’t had people
systematically report tests at other angles, we thing it will work better closer
to vertical, the one concern is driving the bit down into the wood.
 The maslow is very much a ‘just barely good enough’ machine design. there
are lots of things that can make it better, but they add cost and/or size to the