This metod is using lock time, eve uni wiki, and wolfram alpha to calculate target signature radius. Works well for pve since you can optimize missile and fighter performance. Does not work particularly well against player ships sine lock time is only affected by base sig radius of a given hull. Yes MWD does NOT make your ship easier to lock.
Get a ship with low scan res. I recommend t1 hauler with cloak and full rack of warp core stabs. Both scan res and lock time might be capped so watch out for that. Further testing needed.
Position target outside your lock range and attempt to lock. You will fail but note time shown on locking icon. Clicking lock target like mad makes it easy to see cause it only last fraction of second.
Go to wolfram alpha:
your scan res in place of x
lock time in place of y
heres formula if link dies
sinh((200 sqrt(x* y))/(x* y))
If done correctly you will get signature radius of targeted ship