You can fit everything by setting stretch=2 or somesuch, but it will extend the window limits symmetrically.  
plot(md.ca, stretch=2)

Modifying the code of plot.corres() to allow for xlim/ylim adjustment is pretty straight forward. F.ex:
plot.corres <- function (x, main = "", addcol = TRUE, extreme = 0, rcex = 1, 
    rcol = 1, rlabels = "", stretch, ccex = 1, ccol = 2, 
    clabels = "", xlim, ylim, ...) 
{
    if (!is(x, "corres")) 
        stop("argument should be a correspondence object")
    dat = x@data$origOut
    xlimit = range(dat$rproj[, 1])
    ylimit = range(dat$rproj[, 2])
    if (!missing(xlim)) {
        xlimit <- xlim
    }
    if (!missing(ylim)) {
        ylimit <- ylim
    }
    if (!missing(stretch)) {
        xlimit = xlimit * stretch
        ylimit = ylimit * stretch
    } 
    plot(dat$rproj[, 1], dat$rproj[, 2], type = "n", xlim = xlimit, 
        ylim = ylimit, xlab = paste("Factor 1  (", round(x@data$eigenrates[1]/10, 
            1), " %)", sep = ""), ylab = paste("Factor 2  (", 
            round(x@data$eigenrates[2]/10, 1), " %)", sep = ""), ...)
    lines(c(max(dat$rproj[, 1]), min(dat$rproj[, 1])), c(0, 0))
    lines(c(0, 0), c(max(dat$rpro[, 2]), min(dat$rproj[, 2])))
    if (!(main == "")) 
        mtext(main, 3, 1)
    if (length(rcol) == 1) 
        rcol = rep(1, nrow(dat$rproj))
    if (length(rlabels) == 1) 
        rlabels = rownames(x@data$input)
    text(dat$rproj[, 1], dat$rproj[, 2], rlabels, cex = rcex, 
        col = rcol)
    if (addcol) {
        if (length(clabels) == 1) 
            clabels = colnames(x@data$input)
        if (extreme > 0) {
            x = data.frame(dat$cproj[, 1:2])
            extremes = apply(x, 2, quantile, c(extreme, 1 - extreme))
            Accept = as.factor((x[, 2] < extremes[1, 2] | x[, 
                2] > extremes[2, 2]) | (x[, 1] < extremes[1, 
                1] | x[, 1] > extremes[2, 1]))
            text(x[Accept == TRUE, 1], x[Accept == TRUE, 2], 
                clabels[Accept == TRUE], font = 2, cex = ccex, 
                col = ccol)
        }
        else {
            text(dat$cproj[, 1], dat$cproj[, 2], clabels, font = 2, 
                cex = ccex, col = ccol)
        }
    }
}
plot(md.ca, xlim=c(-0.6, 1))

You could ask the author of the function if he could revise it.
His name and contact information is at ?corres.fnc