from what i read of owl bows he makes his hunting bow, which he says is the most stable and durable, 58 inches. if youre testing new waters id say go with 58 inches just to be safe. if it turns out good you can always make another one shorter in the future with all the things you learn while making this one.as far as the working limb and then the rigid tips, you still probably want your working section to be a decent width, so as to keep the stresses spread out a bit over them. no need to make them thin if youre unsure. the static tips are really your choice, but i wouldnt thin the working limb if you shorten the tips. on my bows i keep about 5 inches of my tips thicker so i can thin them later to reduce handshock if it has any, and so i can move nock points if needed. personally id go for 58, leaving the 6 inches of stiff tip. it will give you some more forgiveness in the end, and if you decide later you dont need it all you can always pike it down to 4 inches.make yourself one of the tillering blocks with a pencil and go slowly if the design is unfirmiliar to you, ive found on my recent bow that testing new waters is just that, and this bow has been on the tillering tree for the better part of 4 days to make sure im not being overzealous.