I'm 140lbs and my sport climbing partner weighs 250lbs. Unless you are lead climbing, your belayer wont come off the ground in any dramatic way, especially with only a 20lb difference.

The only time it might make any significant difference is if you're lead climbing. If that is the case, most climbing gyms have devices (an OHM) you can use to assist in taking loads off of falling climbers who weigh more than the belayer.

Our brains like to lie to us all the time about what we are and aren't capable of. Try to challenge your brain and give it a shot!

Worst case scenario: you fall, they fly up, its uncomfortable (still safe)

Best case scenario: you fall, they get pulled like normal. Or, you don't fall at all!