I notice that "as to if" does not follow the pattern:
1) function word x,y
We can't say, "As to if we'll ever get to the bottom of this, there seems to be some doubt," at least it sounds awkward; but it does follow the pattern:
2) y function word x
"There seems to be some doubt as to if we'll ever get to the bottom of this."
I get the feeling that pattern 2 is beginning to replace pattern 1 in general. Does anyone agree? Note that if you want to specify more than one condition, you pretty well have to use pattern 2.
Please send us blah, blah, blah if:
a) blah, blah, blah;
b) blah, blah, blah;
c) blah, blah, blah; or
d) blah, blah, blah.
Imagine reading this

If:
a) blah, blah, blah;
b) blah, blah, blah;
c) blah, blah, blah; or
d) blah, blah, blah,
please send us blah, blah, blah.