I actually prefer the BC (using the hi low offset 3 or 4 inch version) with Push rod inside
This causes the up line, for a bottom mounted Elevator horn, to be the front control line... pull line/Push rod for up but this is just me and I learned it really does not matter
With combat planes the stab/elevator horn is usually on top so UP line is in front...easy to remember
About magnet building... I invested in this method a while back and use the crap out of it even for 100% profile building...I never did invest in all the holding fixtures but do use a Pat king carbon rod wing jig WITH the magnets... and a set of laser triangle squares from Walt....Now if I could just have the eye sight to select a truly straight piece of wood I might get a warp free straight wing
BTW my magnet set came from a supplier WITH holes and two metal side plates on each of the 100 magnets.... many are used without the plates as they are easier to slide around...but for setting ribs square, I use the side plates as they can BOTH hold the rib square, and if pinched tight, hold it upright in height for CA or real good gluing