>.But what about making the cuts accurately ..
>..with the boards laid flat it would seem to be a pain to make
>cuts with the saw held vertically.Alternatively,to stand the board upright
>and make cuts at a 60" height would be awkward also.

For layout,if you have em',  a couple of miter clamps at both corners of
the layed-out joint will  give a simple and solid orientation for marking.

Recently while hand cutting DT's on 6' boards (inside a huge Normite
cabinet shop where I was graciously granted access) the owner saw me
struggling with the vices trying to support the long board along it's
length, and alternately,  somewhat awkwardly clamping the boards
near-vertically to the huge square-cross-section pillars that hold up the
shops ceiling and sawing while standing on a sawhorse (this for cutting the
tails,. btw). He kept casting glances my way and when walking past he would
look on in indulgent stupifaction. Eventually he spoke his mind, wondering
why I was making thing so difficult.
He suggested I clamp the board flat onto the benchtop and then lay on the
floor on my back, positioning myself at the correct relation to the board.
For those that have never tried sawing while laying flat on their back, I
highly recommend  it.  Although I didn't need it, if you need to fine tune
the prone woodworker-to-wood distance, a chaise lounge or low bench should
do the trick, or alternately clamping the board to be cut beneath the
workbench. Many possibilities here.
It worked out so well in fact, that now I have my workbench mounted upside
down on my bedroom ceiling and I do all my woodworking directly from my
bed.

-Neal Weiss
Lurker who will Bio forth after eventually aquiring his first old tool,
hopefully a pre war #4 Stanley in good+ condition (smoother, Jeff) [struck
out twice so far, casting cracks, gah!] to finish his flatfile project.
Nudge, nudge...