It honestly depends on you! I got a C in higher level maths at JC. And i'm not doing too bad in higher maths in LC I'm aiming for a H3. Besides i think its better to at least attempt it because you'll get more points by getting a H4 or H5 even H6 in maths rather than getting a O1 or O2!
It honestly depends on your work rate. I know people who got As and Bs in the JC at higher level and they're finding it tough at the moment. If you're willing to work, there's no reason why you shouldn't attempt it. The important thing is not to become overwhelmed and then dropping because of the fast pace and difficult material. I'm lucky that I've been an A student all along and have kept up the grade due to working at the subject, as the 125 points for a H1 is a real motivator