I have a 155cm proto ctx and I'm 5'9" and weigh around 170-180lbs... It's fine for me, but I think it's really up to what type of riding you'll end up doing most. If you are just riding groomers and wanna do a little park I'd say it's all good. If you are just a pure groomer guy or backcountry riding I'd aim a little longer (upper 150s and low 160s). Just be dedicated to getting to your goal weight cuz you're gonna stay around 200lbs it would be best to stay slightly longer than 155cm in my opinion. I'm just telling you a general guideline, but it's entirely up to your preference. I'm just a little surprised you had a 155cm at 240lbs.