dear sirs

after read a lot, i finally choose the Cabela's Stalker Extreme as my first Carbon Arrows.

everyone said that its a good arrow with a fair price.
so i m moving from my aluminum and fiberglass arrows to stalker ones.

but there is some situations and i need more info

1) i see that there exist two kinds of Cabela's Stalker Extreme Carbon Arrows

the Cabela's Stalker Extreme Carbon Arrows – Blazer Vanes ( Straightness factor to ± .003’’ - IK-417604 and Regular Price: $79.99 )

AND

Cabela's Stalker Extreme Carbon Arrows – Vanes (Straightness factor to ± .005’’, IK-414243 and Regular Price: $69.99)

well, my questions (a, b, c)

a) i dont know if it will be better to get the 0.005 or 0.003 model.
it is important?
or i can pick the cheaper?

b) there are two sizes of this arrow.
Sizes: 55/70 Ibs. (8.4 gpi) and 65/80 lbs. (9.3 gpi).

i shoot a 50 lbs round wheel antique bow.
my draw lenght, from nock valley to shaft front end (with no point) is 31,25 inches (a little long, i know, but it is necessary to my broadheads do not touch the lower part of bow sight).

reading this arrows shaft chart, it is said that i must use a 55/70 size, but, due my long draw lenght, i am right in the upper divisory line to the next recommeded size, the 65/80 lbs (advised to 31 inches shafts at 52lbs, 2 lbs more than my bow )

so, i am afraid to get the 55/70 size and (when put the arrow tip) find i am sub spined due my long shaft or
to get the 65/80 size and find i am over spined due my low poundage bow.

so i came with an idea:

- get the 65/80 stiffer arrow and find the correct setup just changing the field point from 85 to 125 grains point models, till i find the correct setup to this stiffer arrow.

is it a good idea or i need to stick with the 55/70 size?

c) i read some texts about this model of arrow and see that some people say that (when adjusting the shaf lenght) is a good thing not only cut the front end of shaft but the rear end too in order to get a true spin.

i did not get this.
cut both endes to get a true spin?

would you please explain it?
what it the benefit of buy a complete arrow with nock and fletch and remove the nock and fletch to cut both arrow ends and them renock and refletch?
how can this grant a better flight?

as always, thanks a lot

cheers from brasil.