In theory it is OK (same as MP3). However, it might depend on implementations.
At least encoder has to be able to eat float PCM. Same for decoder.
I tried this before with fb2k + qaac, and it was fine. It had peak of 1.6 or so, and peak was preserved.
Of course you have to set the maximum bitdepth to 32 on CLI encoder setting of fb2k.
If you want to check the decoded result, just convert to WAV with fb2k (also specify 32bit here).
In my case, I quickly looked at the decoded result with some Python scripting like the following:
import struct
wavdata = open('foo.wav', 'rb').read()
wavdata = wavdata[44:] # chop off the header. might be different on your case
pcm = struct.unpack('f' * (len(wavdata)/4), wavdata) # parse as float32 sequence
pcm = map(abs, pcm) # convert to abs values
print 'peak: %g, avg: %g' % (max(pcm), sum(pcm)/len(pcm))
If you want to see just the peak of it, probably scanning with replaygain is enough.