Secondary double glazing for patio doors?

Hi,
I have a largish patio door (approx 270cm x 207cm) which already has aluminum double-glazing (two equal size panels, one fixed one sliding). I want to improve the sound insulation (noisy road nearby) and I am considering adding secondary glazing for this.
I would like to maintain the same design (two doors) so each panel will be approx 200cm x 130cm. Is this possible - these would be large sheets of glass? Could I use plastic sheeting instead? Would it have a similar sound deadening effect as glass?
Finally, does anyone make such large aluminium secondary units? I guess it would have to be aluminium even if I used plastic glazing.
Thanks for any info,
John Smith.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.