I doubt that applying wood trim over a pre-textured panel will look like anything other that what it is: a poor simulation of half timbering. To be visually effective the plaster finish must contact the wood so it looks like an infill between posts/beams.

I believe the interior finish you are trying to simulate is more likely to be a smooth plaster.

Thanks, but this is my basement, that people can tell my cinderblock basement is not really beam and stucco isn't such a big deal. I just want something easy to put up that creates little mess during install because the basement has to remain functionally usable during the entire install.

I may just use flat interior wood paneling instead of the thicker (and variable thickness) exterior hardboard siding. It's cheap, easy, looks good enough for what I want.

You might consider 3/8" t-1-11 plywood with no grooves. Its an exterior grade plywood but you could do some creative trim work in the feild and the perimeters to give a rustic look to go with the beam work. The ply has a rough sawn facing that looks good with various finishes such as solid or transperent stains, wood species stains, painted, or even finished as is.

I wouldn't use these to side my house, but for your architectural indoor look:

http://www.genstoneproducts.com/stucco.cfm

http://www.custompanelsystems.com/

http://www.lpcorp.com/sidingtrim/lpsmartside/products/panel.aspx

Most are 4x8 or 4x10 sheets. I'd screw them to the studs like drywall and put some construction adhesive on too. Then just mix a small batch of stucco mortar to cover the screw heads. Where the beams meet, use a grout bag to fill the gap to the beam and smooth with a trowel. Similar to caulking trim. Then paint the whole panel.