I think you're overthinking it. I've eyeballed the stems on my 3 Yost boats. Don't bother with laying the parts on the floor, because the position in relation to the 2 gunwales will have more to do with alignment than position in relation to the keel strip.

: Hey All - I'm working on a Sea Ranger frame and would like some
: suggestions on a few things.

: The stem/stern blocks; how do you ensure that they are perfectly
: perpendicular to the keel with the boat still mounted in the
: strongback?

: The only/best approach I can see is to take the keel off of the
: mount and lay it on the floor and install from there.

: Any ideas?

: Eric