Glass Conservatory roof

I need some advice on installing a glass conservatory roof. I am designing a glass roof which will be 4000 mm long and 4 mm thick and approx 700 mm wide. From some research it looks like I will have to join this roof together as a 4000 mm double glazed unit will be hard to buy and heavy to install.

Can anyone advice me on the best way to join these units so I get a good water tight joint.

I have looked online and can only find some joining bars on ebay link below
http://www.ebay.co.uk/itm/24-25mm-M...hash=item5692c9ce9f:m:mp8OF1L25HVMWA55ksYZzYg

Is this the best way and are there better suppliers online.

I think I have now found my answer in the web, muntin bar will do the job. I have another question if any one has a glass roof what thickness would the glass be. I think 4mm is ok below 6 m in height and what is the best spacing between sheets