Is there a way in R to customize the height proportion of graphs without using the heights statement within layout?

Question

Here is the code I'm starting with.

par(mar = c(2, 2, 2, 1),
mgp = c(1.1, 0.15, 0),
tck = -0.01)
a <- rnorm(500)
layout(mat = matrix(c(2, 2,
1, 3), 2, byrow = TRUE),
widths = c(2, 1),
heights = c(3, 2))
plot(a)
hist(a)
boxplot(a)

I was wondering if there is a way to change the graph proportions without using widths and heights. I figured out that I could do mat = matrix(c(2,2,2,1,1,3) to change the column ratio, but I'm not sure about the heights. Any help is appreciated!