Rgraphviz overlap of nodes and edges

Hi,
I plot graphs on small  diagrams. With colored  or thick edge lines then 
the nodes and the edges overlap. The edge line overwrites the nodes 
which looks ugly.

What can be done about that? I already tried to change the sep attribute 
with no effect.

Thanks,
Franz Quehenberger

V <- letters[1:10]
M <- 1:4
g1 <- randomGraph(V, M, .2)
z <- getDefaultAttrs()
z$edge$color="red"
z$edge$weight=5
plot(g1,"neato",attrs=z)