Well my wheels haven't fallen off yet :ROFL: I've run a set of these on my daily driver for about 10 years, and I also have a set of adapters in the same design to run the Q7 20s on my S8.

The wheel bolt threads in to a steel insert which is pressed in to the alloy spacer from behind. The insert is as thick as the car's hub so no less strong +++

14mm x 70mm...
No problem!

The load on wheel bolts is in tension.
Provided they are torqued correctly there is no shear load, and almost no bending moment. All shear load is born by friction on the mounting surfaces, even during acceleration and braking.

A 14mm x 50mm bolt will not have any significant increase in twist (along the shaft) compared with a 14mm x 70mm bolt either, and the tensile load they can withstand is equal.

If you're using hub centric spacers, they will centre the wheel on the hub properly making sure the bolts align.

trouble is i cant find any 70mm ones anywer

Are the Merc wheels taper or radius seat? There are four listings for M14x1.5 x 70 with taper seats on ebay.

I've used this guy before for wheel nuts and bolts - very knowledgable
http://www.speedshack.co.uk/Wheelnuts.htm +++

merc are radius bolts but different to Audi

speedshack longest 64mm NO stock special order

no problem if not using spacers straight on with the merc standard bolts

this is how it looks at the moment
 

perfect setup right now and the odd 5mm makes a big difference in looks

http://i64.tinypic.com/dovza1.jpg

ive decided to sell these lovely Mercedes wheel that are now fitted with brand new tyres so i will list them on here first..

http://i63.tinypic.com/205f910.jpg

You can only have them if you slam it and wear the hoodie and have the chimpanzee swagger to match