WP Effects on an Armored Target

[Raellus]

If you play in my PbP, be forewarned, there are SPOILERS ahead.



I need some advice on how to resolve a recent development in my PbP campaign. I just rolled a natural 1 for a 120mm mortar strike on a landing craft converted into an armored monitor (styled on the ones the U.S. Brown Water Navy used on the major river systems of South Vietnam). The hit location is the hull and the round type is WP. Since the terminal trajectory of the mortar round would have been straight down, I've interpreted this to mean the the mortar round struck the top deck between the monitor's main gun (mounted over what used to the be the troop compartment) and the superstructure/bridge. Besides blinding the bridge crew for a while, I'm not sure what kind of damage this would have done to the vessel itself. The area the round struck isn't really armored, it's just roofed over with thin sheet metal.

Would the round have punched through before exploding?
Would it have exploded on contact?
In the case of the latter (which I assume to be the likely result), would the explosion have ruptured the roof? I assume it would, to some degree.
Could WP fragments burn through thin sheet metal?
Could WP fragments set dried paint on fire?

I'm just not sure how much damage the impact and explosion of the WP bomb would do. If it was a HE round that hit, I think I'd have an easier time of it. I've read that 120mm HE mortar bombs are at least as destructive as 105-123mm tube artillery HE shells. My impression of WP artillery rounds is that they don't so much explode as they burst. This may seem like a spurious distinction, but I think it would make somewhat of a difference in terms of the resulting blast/penetration effects. I want to handle this realistically. Would the monitor be knocked out of commission by a 120mm WP hit, or could it shrug it off the damage caused by the impact/bursting? Either way, the chemical smoke and incindiary effects of the WP will have to be dealt with but I feel confident that I can handle those fairly realistically.

Thanks in advance for your help.