Instead of playing on an 8' stop, try a 4' registration one octave lower. 4' octave might be just what you need instead of an 8' principal. Likewise, a 4' flute might would sound much better in comparison of an 8' flute for your piece.
You can try building an entire stop combination based on a 4' pitch level played one octave lower. This works when the mixtures are too harsh and too high but you need a full principal chorus.
For example, instead of principals 16', 8', 4', 2 2/3', 2', 1 1/3', and a mixture of 1' basis, try using the same stops but without the 16' and play one octave lower. This way the sound will become fuller and easier on your ears because the mixture will be based on 2'. For this trick to work, though, the manual part of the piece in the original should not descend lower than the tenor C because when you drop it one octave lower, you will go beyond the bass C.
A 4' octave played lower often work for the left hand of the trio sonata or for the right hand solo part of the chorale prelude. Flutes 4' and 1 1/3' sounding one octave lower would produce the same effect as flutes 8' and 2 2/3'. This is especially useful when 2 2/3' is a principal stop but you need a flute-based mutation.
Or consider this: in a chorale prelude with the ornamented right-hand part you would want to use flutes 8', 4', and 2 2/3'. Compare this combination to flutes 4', 2', and 1 1/3' played one octave lower. Maybe the balance of parts would sound better on your organ when you try playing together with the accompaniment on a softer registration?
Remember, even the ugliest organs have at least one decent stop. Often - that's a stop of a 4' pitch level.