[XeTeX] Arabic fonts and line heights

[Nathan Camillo Sidoli]

This may not actually be a xetex question, but I suspect I may get a 
useful answer here.

Is there someway I can more accurately control the line height when 
using an Arabic font? When I use certain Arabic fonts, such as Amiri, 
which stack a lot in certain situations, I get very mixed line heights. 
The effect of this is that in entire pages of Arabic some lines are 
bunched together and others are more spread out, while in pages where 
Arabic words are quoted and phrases in generally English text the will 
sometimes create large gaps between the lines. I can get rid of this 
effect by correcting with something like scale=.8, but this makes the 
Arabic text so small as to be almost unreadable.

Is there some way I can force the text to observe certain line heights, 
or at least make them all the same on each individual page?

Thanks,

Nathan