I'm shooting a lighter arrow this year. A 2212 aluminum arrow out of my 42# and 37# bows. Both of my bows have a 2 bundle 12 strand Dyna97 fast flight bowstring.
Last year I was shooting a 602 grain 2117 out of my 42# bow and it gave me a 14.33 GPP arrow. Shooting a 535 grain 2114 out of my 37# bow gave me a 14.45 GPP arrow.
This year, shooting a much lighter 421 grain 2212 out of my 42# bow gives me a 10.02 GPP arrow. Shooting the same 421 grain 2212 arrow out of my 37# bow gives me a 11.37 GPP arrow.
I can shoot the same 2212 arrow out of both bows because the brace height is different for each bow. For the 42# bow, the brace height is 7 15/16" and for the 37# bow, the brace height is 8 3/8".
If your bow can handle a fast flight bowstring, I say go for it. A 9.3 GPP arrow shot out of a 55# bow is going to be heavy enough and it's going to be fast enough in terms of fps. That arrow should easily dispatch an elk.