New Ductwork Sizing

I had a new furnace installed last year and unfortunaly could not afford the ductwork portion. I know my trunks are grossly undersized and would like to replace them. I have done some calculating and it seems the other ducts are sized right but I would like to investigate further. Could anyone point me in the right direction. Any reference books I might look through or a Manual D worksheet perhaps. Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This company offers trial software that you should be able to use to check your sizing! http://www.elitesoft.com/web/homepage/elite_demo_list.html
Wayne

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.