lsmeans custom contrast simple

require(lsmeans)
data(md_12.1, package = "afex")  # data from Maxwell & Delaney (2004)
options(contrasts = c("contr.sum", "contr.poly"))

str(md_12.1)

a1 <- aov(rt~angle*noise+Error(id/(angle*noise)), md_12.1)
summary(a1)  # main effects and interaction match table 12.5 (p. 578)

(c1 <- lsmeans(a1, ~angle+noise))

contrast(c1, method = list(
  abs_04_vs_8 = c(1, 1, -2, rep (0, 3))/2,
  pres_04_vs_8 = c(rep (0, 3), 1, 1, -2)/2
  ))