If its rad is as susceptible as I remember, I'm not sure the 152 will really like this niche. Not if the 29 is as fast as it seems to be, and has about twice as many guns as the B-17s do.
From memory of what a B-17 is like, and what it'd be like if it got this much extra speed and guns, you'd have to be very well practiced and disciplined to successfully take down B-29 formations. Success = taking no critical damage. IE at the very least taking critical damage only after the formation is down.
So it's finally a target that's actually like what the 152 was meant for, but IMHO a sweet & sour deal. One natural and positive solution I see is that this encourages better teamwork. Two or three 152s should be enough for successfully dealing with B-29s. That's a fair setup for the 152 - it'd still be a good challenge.