I can't find the original notes, but here is how Eric 
and I play the Raptor 1NT Overcall. -H.Eng, 21 Oct 2001

                Raptor 1NT Overcall
                ===================

After an opening one level bid, a 1NT overcall shows at
least a four card major and a five card minor.  The minor
is longer than the major; with the same length, we use a 
Michaels overcall.  One of the suits is always known: over
1H/1S, 1NT shows the other major and an unknown minor; over
1C/1D, 1NT shows the other minor and an unknown major.  The 
Raptor 1NT shows regular overcall strength -- for us, that 
means we have enough strength for wanting the known suit 
led.  If you like sound overcalls, then probably you'll 
need at least 10 hcp.  

I'm not sure if these are the standard responses, but here 
are the responses that Eric and I prefer to play.  After 
1NT over a minor opening,  
  signoffs: 
    * two of the known other minor, 
    * two of a major, although opener can raise with four 
       and a non minimum (~5 losers)

  relays to find out the unknown major: 
    * two of opener's minor is weak
    * 2NT is strong.  Overcaller rebids 3C/3D with minimum 
       and the corresponding suit (C=H, D=S).  With a 
       maximum, overcaller rebids 3H/3S.  

  other bids:
    * three of the known other minor is invitational
    * 3NT is to play
     
After 1NT over a major opening, the relays are now:
    * 2C as pass or correct for overcaller's minor  
    * two of opener's major is strong.  Overcaller rebids 
       in steps: 1st (min, lower suit), 2nd (min, higher 
       suit), 3rd (max, lower suit), 4th (max, higher suit).


Variations
----------

Some people play 2H asks for the major after 1C/1D-1NT, 

Also, some play that a 1NT overcall doesn't necessarily
guarantee 4-5 distribution.  You could overcall 1NT after 
1H with just three robust spades: KQx/x/AQJxxx/xxx (S/H/D/C).