I did one of the Harar that I had which was MAO Blue Horse variety, not the Longberry one, basically the aim I had was to pull the roast just shy of second crack.
I dont think pre-heating the corretto makes a difference but in this particular roast I pre-heated the BM chamber for 3 minutes on a low HG setting and loaded the beans when the probe in the empty chamber was showing 127 degrees.
The temp then dropped to 60.6 C and then started rising again. FC has hardly discernible and happened somewhere between the 11 and 12 minute mark and I pulled the roast just before the 17 minute mark at the temp of 218.6 C (before SC).
Being a light roast I expected some acidity but I was very pleasantly surprised to get distinct chocolate flavours instead which Id normally expect to get with darker roasts.
Dont know if it will work for the harrar longberry but Id be looking to replicate that for my harar roasts.