Yes, as long as you have distance the RED model could do that.
Remember you need to work out "close" measurements with your opponent but I have always played if a corner reaches then the model is in HTH. You want to also "attempt" to base them together but with terrain and etc that is to always possible but nor should it allow someone to allow 15 models to attack one model on a 20-25mm base.
To clarrify the corner issue, I do believe it was argued several times on the past 2 Mordheim SG forums and corners do count working off a standard from WHFB where corners count if properly aligned. This means, if 8 models can see a standard 25mm base (A) and they are on 25mm bases then all 8 models could charge the target model (A). Remember though that they have to engage the enemy in the most direct way, so a certain level of finesse is required in this as if you charge the wrong person first then other people may be unable to charge the opponent despite seeing the target (A) at the beginning of thje turn for the charges. This is because you have to charge via the most direct path, so if you charge someone closer in first then you risk characters further away not having the movement to reach further away. Making use of the leap Speed skill is a great way to abuse this if you have it as you are able to move people in to the front and then just leap straight over the top to get in behind, bypassing difficult terrain and other obstacles that would otherwise make a charge impossible.
In the same manner, charging a larger based monster, so long as you have it all set up and moved properly, enables you to get quite a few more then just 8 characters into base to base contact for attacks. In this case, the one thing I have always wanted to see but have yet to witness is a large based monster like an ogre in a multiplayer game get charged by 8 other monstrous creatures (large targets I mean)...that'd be hilarious.
To the first point on a stunned model and a standing up model, if botha re in base contact then the corner ruling to maximise attacks on characters would see the player facing the stunned player but corner to corner with the standing up player, having to direct all his attacks at the standing warrior and ignore the easier to kill stunned character also in base contact until the next combat round. Splitting of attacks is not allowed by the rules IIRC. The exception to this would be spines on a mutant or possessed or possessed hero with a gift of The Shadowlord. The spines automatically hit every model in base contact friend or foe first before any blows are struck. Thus you would get your friend in base contact with you, the standing up model in base contact with you, and the stunned character in base contact with you, resulting in the stunned model instantly going out of action (awesome free experience!) and your friend and the enemy taking a strength 1 hit. If you're lucky, the standing model gets knocked down and when it comes time to attack the model now knocked down counts as knocked down so you would only need to wound the model to knock it out of action (or if it was stunned by the strength 1 hit of the spines, auto-out of action). Does that makes sense?
Cheers,
Ram.
