Trailer cable connection...HELP

I'm hoping someone else has gone through this scenario or knows something that can help me.

I bought the most incredible X2. Absolutely gorgeous boat!!!!!

I go to hook it up at the dealers and low and behold I've got the wrong trailer cable connection for the lights and brakes.

Here goes.... I've got a land rover discovery. The trailer connection is a 7-pin but its round
In order to tow my old boat Land rover sells an adapter that turns it into a 4-pin.

My new boat has this weird looking 7pin but its flat( kind of like a n RV hook up.)

I phoned 3 land rover dealers there is no such thing as 7pin flat from land rover. How do sell a 4X4 that can't tow 90% of trailers with brakes!!!!!!!! Well that's my fault...although i can honestly say I didn't plan on buying such a large boat 2 years ago.

WHAT DO I DO NOW????? (I'm not selling my truck...for the smarta@%&$%)
The service guy at the dealer did a Mcguyver with some gum, spit, a 4 pin to 7flat adapter from NAPA autoparts, and small steel rod stuffed in the hitch to prevent the brakes from coming on when I back up.

So now I have a 7-pin round--too--4pin adapter---too---4pinadapter---too---7flat----too---the 7flat trailer
I take the steel rod out when driving but when I step on brakes to slow down the brakes on the trailer vibrate pretty rough. (can't be good)

I know nothing about trailer brakes.

Of course there's nothing in the mastercraft owners manual. I guess they figure we all live on the water with private slips.

I called one shop that said I need to add something on the dash with a switch, one shop said it can't be done, one said it would ruin my truck....

I'm open to any suggestions.

Thanks guys!
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