Fairly typical outcome for SHG and SHB varietals mate, when youre used to roasting lower altitude (softer) beans.
Best thing to do is to slow the roast down somewhat, probably in the region of 14 minutes to reach Rolling First Crack (RFC), reduce the heat input once RFC is very active so that the thermal gradient of the beans mass is down to 2.5-3C/Minute. This should have you at the start of Second Crack (SC) about 5-6 minutes after the heat adjustment. Its entirely personal but for my palate I pull the roast after Rolling Second Crack (RSC) is starting to get a head of steam up and then immediately dump and cool.
Have also discovered that (for me) a resting period of 5 days or more really allows the flavours to develop but you may enjoy something a bit different so start tasting after a couple of days and note the changes observed as each day passes. Hope this is helpful "sd"... :)
All the best,