Brendan, not to be facetious, but why is weight a big consideration for you? (Small locomotive or tough grades?) Especially if you're running disconnect-style log trucks, MORE weight may help them track better.
Real "logs" (in my case, cuttings from limbs pruned off our large maple tree) may not be overly heavy unless you're using an especially dense wood (such as maybe oak?). They are often "free"
as well - & like using finely-ground real coal in your locomotive tenders, it's hard to beat the real thing for realism.
My mainline has a ruling grade of 3%, a my live-steam Shay can handle a 5 or 6 car train of "real" logs easily:
The grade is a bit more apparent at the start of this clip (same train):
If you still don't want real logs, the Bachmann plastic logs are lighter, & I think I've seen some people paint them up to be a bit more realistic. Hope that helps!