A posteriori change of text size in ggpairs

Hi,

My question is about setting the font size in the panels of the upper triangle of ggpairs which report correlations between continuous variables.
I know how to do that upon creation of the ggpairs object (ie, pm2 in the code below). However, I would like to be able to do that after the creation of the object (ie, pm1 in the code below). Any suggestion to modify the object after its creation?

require(GGally)
#> Loading required package: GGally
pm1 <- ggpairs(iris, 1:3)
pm1

pm2 <- ggpairs(iris, 1:3, upper = list(continuous = wrap('cor', size = 2)) )
pm2