I haven't run into this condition myself when using upsample, but if I get a chance I'll try to reproduce it so I understand the situation. I assume this +5dB that you're seeing is in addition to the level variations that exists between DVD (which is mixed at a lower level than CD to provide more response range) and formats like CD, VHS, and cable (which are mixed "hotter" to sound "better" even though it can lead to them clipping sooner).