Alright. I gotta point this out as it's been happening quite often when I use this upgrade...
The projectile HP of the Billy, since it has such low HP, (literally 4 HP), there is a chance that random fire will destroy it before it hits its target. I've seen a PD randomly shoot and accidentally destroy it, I've seen ASF randomly shoot and destroy it, I've seen the beam of a Monkeylord and GC kill it, and I've seen Harbs' & Brick fire kill it. Heck, I've even seen a torpedo kill it, too!
Wouldn't it be of benefit to increase the HP of the projectile drastically and increase the damage of the TMD to match?
TMD would deal 50 damage and standard missiles would have 50 hp, the damage from the TMD kills the missile in one shot - no change here.
If the Billy has 151 HP, it would still tank 3 shots with the 4th killing it.
This change would mirror the Nuke Missile HP change that was made a while back - to prevent it from being shot down by random fire as it is fired or as it is landing.