What is the maximum takeoff weight allowed for a part 103 ultralight?
14 CFR 103.1

The FAA currently does not discriminate between "VTOL" and "normal" ultralight aircraft, nor between gas-powered or electric. The aircraft, if powered, cannot weigh more than 254lbs "empty" weight excluding floats and safety equipment that deploys in an emergency situation.

I'm not sure what you mean by "peak limit" or "continuous operation". The aircraft, when weighed without liquid fuel, must be less than 254lbs. It can carry up to 5 US-gallons of fuel (which can add up to 30lbs).  

There is no limit to the MTOW for the aircraft though, it can carry a 400lb individual if you can make it fly, but it can't carry more than 1 person. So if the aircraft weighed 253lbs, you were 400, fuel is 30 that is 683lbs and still legal under Part 103. (Depending on how liberally you want to apply the "single occupant" rule, you may try to squeak your 200lb Mastiff aboard as well)