Flopped 2 Pair, Bad Underbet?

[Neill]

Stars 3-table 5+.50

Villain is extremely aggressive. I had been quiet for a while, and the table had gone tight; so I decided to try a blind steal. When I flopped the "monster", I was thinking double-up. Should the flop bet be bigger?

PokerStars No-Limit Hold'em Tourney, Big Blind is t400 (9 handed) converter

saw flop|<font color="#C00000">saw showdown</font>

MP3 (t7845)
CO (t525)
Button (t4465)
SB (t4055)
<font color="#C00000">BB (t9600)</font>
UTG (t2550)
UTG+1 (t2100)
MP1 (t4110)
<font color="#C00000">Hero (t5250)</font>

Preflop: Hero is MP2 with 6[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/spade.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">Hero raises to t800</font>, <font color="#666666">4 folds</font>, BB calls t400.

Flop: (t1400) K[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets t1000</font>, BB calls t1000.

Turn: (t3400) 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets t2000</font>, <font color="#CC3333">BB raises to t4000</font>, Hero calls t1425 (All-In).

River: (t10825) Q[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players, 1 all-in)</font>

Final Pot: t10825
<font color="#009B00">Main Pot: t10250 (t10250), between BB and Hero.</font> &gt; <font color="#FFFFFF">Pot won by BB (t10250).</font>
<font color="#009B00">Pot 2: t575 (t575), returned to BB.</font>

Results in white below: <font color="#FFFFFF">
BB has 9c 8c (straight, nine high).
Hero has 6h 7s (two pair, sevens and sixes).
Outcome: BB wins t10825. </font>