I have somewhat of the same issue, and today I'm roasting a sample for Milowebailey that's only 4oz.
The temp probe becomes more useless as bean mass decreases, since the tip of the probe where it reads temps is exposed to more hot air and less beans. (Sort of like Tex - more hot air and less beans
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Your main concern tho' will be to learn to modulate your heat, with or without the assistance of the thermometer. Small roasts are a two-edged sword; they're easier because they'll accept heat more easily and can be raised quickly, but harder because they have little momentum and won't coast as nicely- if you kill the heat the beans cool/stall easily.
All I can suggest is finding a way to get the probe to stay in the same spot without having to hold it, and then watch the temp it reads just as first starts and then modulate the heat so that temps climb gradually. Somewhere towards the end of 1st you should be able to turn the heat off for say 15sec., while watching the temp- the temps will continue to climb because of the beans' momentum and being exothermic, but that rise will slow. As the temp rise slows, turn the heat back on, allowing for the amount of time it takes for the heating element to come up to temp and start adding more heat into the beans.
With practice you'll be creating a nice, even, and slow heat ramp through 1st, and into 2nd.
You may be dealing with another issue too. If too much heat is poured into the beans going into and during 1st, they will have too much stored energy and will continue to climb right into 2nd, regardless of having the heat off. I have fun watching my temps climb an extra 10deg or more, after killing the heat. In fact, that's often how I end a FC or FC+ roast; say 1st is ending around 420F and I let the roast hang around the low to mid 420's for a couple minutes (which would give me a nice C+ roast level) and then I add heat until my probe reads 426, if I kill the heat then it'll climb all by itself into the mid 430's with an outlier snap or two of 2nd crack. So make sure that you don't pour too much heat into the roast, and then expect it to stop when you want it too.
Hope that helps answer your question. Sorry if it's too much info.