The tuning aid can only measure SWR where it is located.  Since the
purpose of a tuner is to lie to the final amplifier, as close to that will
give you the most accurate results.  I have a home brew job that was
designed to go across the SWR bridge.  Now if you put it across a watt
meter instead, you eliminate the problem of getting different sensitivities
on different bands with the same power.  I put a jack in my versa-tuner,
and put the leads across the sensitivity pot.  Nothing bad happens on
higher power, because the aid gets nothing more than the watt meter gets,
and neither of them have blown.  You will however need to turn down
sensitivity indicator, because maximum pitch is very easy to achieve.  On
the other hand can tune qrp signals as well.