An attenuator will also lower the download power levels, though, so be careful of that. Though if your download power levels are too high, that might be a good thing.
As long as the download SNR and power levels are good, don't sweat the upload power levels being too low. The node tells the modem how strong a signal to use, so if the node can't understand the modem, it will tell it to up the power level. If all it takes for the node to hear the modem is 39 or 35 or whatever, that's not a problem in itself.