This is an excellent effect. My one criticism is that the two routines (with and without the
magnetic gimmick) should use a very different card. Mine uses a two
of spades and two of clubs.
If you do strolling magic, some people may see you
perform twice--and might assume it is the
same card each time, thus destroying
any assumption they get a free choice. The two cards should
be different colors
or at least a two of clubs and a five or seven of spades.
Consider
this if you intend to make more copies.