Intercooler is it going to be to big???HELP!!!

I have just got a cooler for my 300tdi disco but its a bit bigger then I thought I !!
Its 300 wide and about. 800 long the inlet/outlet and on the same side tho !
With a bit of welding and changing the inlet/outlet position so it comes out the side of the cooler not the end it will fit . But can any one tell me how will it effect my engine will it be too big and make the turbo lag too much ? I am going to turn up the turbo and the pump. Has any one fitted any cloolers this big and what sort of gains did you get ? ??
Grrrr need some help befor I spend more money getting it rewelding and getting all the pipes to make it fit .... Or am I Wasting my time and money. ????

Have a search its bin covered with a how to make it fit guide, something like budget intercooler

Here http://www.landyzone.co.uk/lz/f8/economy-intercooler-diy-233678.html

Thanks for the link mate do you think that the cooler I got will be to big and I will get a lot of turbo lag ??