earth for leven jump start kit

[shropshire lad]

I am fitting the Leven JSC1 jump start kit to my '98 Chimaera , which seems quite simple .
They advise using the front earth where the body fixes to the chassis on the driver's side , also earthed here are the lights , horn etc. However it is a pig to get at , "the bible " even suggests that cutting a piece out of the bodywork is necessary to get at this earth.
My question is ,what about the earth just in front of the driver's footwell ? Access could not be simpler and it is a good earth as far as I can see. The only issue would be dirt but if its clean to start with and I keep an eye on it surely its a good solution. Anyone know why Leven recommend the front earth , or any reason why I should not use the easy one. (Tried phoning Leven but have given up - has been engaged for ages )
Thanks.

[shropshire lad]

OK - have solved the problem by eventually getting through to Leven . Very helpful too- and the good news is that its fine to use the earth in front of the footwell - the easy one.
Right then - wheres that spanner