Minor improvements to gameplay tips section.

doc/sopwith.6

@@ -119,15 +119,15 @@ The machine gun can be used to destroy ground targets as well as planes. Some
 targets at the edges of the map are much easier to destroy in this way. Since
 the machine gun has a limited range, reducing your speed when attacking a
 ground target can give you more time to aim and attack before you have to pull
-away.
+away. But don't reduce the speed too much or the plane may stall.
 .IP \(bu
 Computer planes will try to tail you so that they can shoot you down. Don't
 allow them to get a clear shot. "Wiggling" the plane by repeatedly pulling up
 and down can be an effective evasive maneuver.
 .IP \(bu
 Firing your machine gun through a flock of birds will cause the birds to
 disperse, and the computer planes will sometimes hit a bird and crash. However,
-this tactic can also backfire.
+this tactic can also backfire for obvious reasons.
 .IP \(bu
 Each computer plane has a "territory" and if you escape that territory they
 will break off their pursuit. At the boundary between territories you can
@@ -142,6 +142,9 @@ break out of the stall before your plane crashes into the ground.
 .IP \(bu
 Wait until you're close to your base with a clear path to the runway before
 pressing the home key - the autopilot sometimes makes mistakes.
+.IP \(bu
+It's possible to fly upside down, but trying to drop bombs while inverted is
+usually unwise.
 .
 .SH MEDALS
 .