RecordPlot

I want to do a zoom with recordPlot(). I have problems with lists.
(R-2.0.1 patched 2004-11-30 , various linux). I have problems 
with RecordPlot class structure.

plot(1:10)
saveP <- recordPlot()
dev.off()

sx <- saveP[[1]][[2]][[2]] 
saveP[[1]][[2]][[2]] <- sx 

Error in "[[<-"(`*tmp*`, 1, value = list(list(
.Primitive("plot.new")), list(.Primitive("plot
.window"), c(1,  : 
        incompatible types

typeof(saveP[[1]][[2]][[2]])

[1] "double"

typeof(sx)

[1] "double"
        

But:

s1 <- saveP[[1]]
s1[[2]][[2]] <- c(4,6)
saveP[1] <- list(s1)
saveP                  # zoom is OK

Also, I don't understand recursive indexing.
With not modified saveP,

saveP[[c(1,2)]]

[[1]]
.Primitive("plot.window")

[[2]]
[1]  1 10

[[3]]
[1]  1 10

[[4]]
[1] ""

[[5]]
[1] NA

# OK

saveP[[c(1,2,2)]]

Error: recursive indexing failed at level 2  

# why not [1]  1 10 ??

Jean Coursol