Getting ready for Enfilade

The local convention Enfilade is coming up in May and I have decided again this year to run a game.  This year I want to do a portion of the Battle of Germantown.  I say a portion because the battle itself was a large battle, almost 11,000 men of Washington's army and some 9,000 British under Cornwallis faced off against each other.  It also raged over a large area which you can see from the map from GMT's game The Battle of Germantown.  

If I tried to recreate this entire map it would end up covering several tables etc... So I've decided to narrow the focus of the game to the battle around the Chew House where the 40th Foot (about 120 men) had barricaded itself inside and turned it into a fortress.  Meanwhile the Americans attacked it again and again with poor results.  Washington heeded Knox's advice to not bypass the house, so the house became the focal point of the battle.  All the while Anthony Wayne and Greene had pushed on were engaged with main British army. What I'm thinking about for objectives for the game will be the Americans will have to retreat off of the table (lengthwise), the British will have to prevent the Americans from retreating or capture/kill more units than the Americans can retreat and save the 40th foot.

Here's a close up of the area I'm thinking about covering.  The table I have is 5'x8' at the convention. The house will be the center of the table. The game will be played along the length of the table. The rivers will be the borders that run the width of the table.  The Gorga's Lane and Bristol Road will finish the square.

The terrain should be fairly easy to produce.  I have most of the houses and one large enough for the Chew House.  Also, I have enough terrain to make the ridges.

Well that's my idea for Enfilade.  I'm not 100% sure on the victory conditions.  I'm not sure if they will work yet.  Any suggestions?