I agree with Guy on the Oboe d'amore being a very different instrument. I was thinking at a basic compostional level, one might want to write for that instead of oboe. But you certainly cannot play an oboe solo with oboe d'amore as they are totally different instruments.
On the french horn I never noticed any problem with the solo, and in fact love it. The triple horn has a deeper tone, and is another wonderful sound, but the regular solo f horn has a beautiful tone I wish I had obtained in my years of practice and performance as a horn player [:'(] Also, the regular f horn is a crossfade sustain instrument, which is huge for the lazy MIDI orchestrator!
On the french horn I never noticed any problem with the solo, and in fact love it. The triple horn has a deeper tone, and is another wonderful sound, but the regular solo f horn has a beautiful tone I wish I had obtained in my years of practice and performance as a horn player [:'(] Also, the regular f horn is a crossfade sustain instrument, which is huge for the lazy MIDI orchestrator!