Maximum span/strength of Howe Truss
Trusses are designed based on 1) top and bottom chord size, 2) size of web members, 3) size of connectors at each chord, 4) species of wood, 5) pitch of roof.

I'd go to your local truss manufacturer and give him all the info I listed above and have him run it through his "truss calculator". It'll take him about 5 seconds and you'll know for sure. (Or, go to your local truss manufacturer and ask him to run a printout for 4:12 truss spanning 25'-7" out to out and take the printout home and compare.) 

You will be able to compare everything fairly easily, except the connector plates pressed into the chord joints. For that, ask to measure one of their standard steel plates and measure distances between deformations and depth of deformations.