I would like the blank to me inbetween 9-12 foot Thanks

I make custom rods, and have made several fly/spin combos. To select a blank, do the following:

(1) Choose the fly line weight you wish to use on the rod. (For example, a wt 6 line.)
(2) Choose a spinning lure weight you wish to use. (For example, 3/8 oz.)
(3) Determine the weight of the fly rod's line (wt 6 in example) in ounces. (The first 30 feet of a wt 6 line weighs about 1/4 oz; a wt 8 line about 3/8 oz.)
(4) If the fly line weight and lure weight are relatively close, the blank will work for a fly/spin combo. (In this case, it probably would work; if you wanted a 3/4 oz lure, it would NOT work.)
(5) Now select a spinning blank for that lure weight in the length and action you want. (From my experience, a spinning blank will make a better fly/spin combo than a fly rod blank.)

Hope this helps!

Thanks whould youi help
(1)i want to use a 8 wt fly line
(2)i would use about 5 oz
(3)the weight of the fly line is 3/9oz
(4)not sure????
(5)9ft-12ft. 12 preferably medium to extra fast preferably medium

so could you tell me which blank to use

No fly rod blank will carry 5 oz., even heavy salmon rod blanks and many surf blanks won't either. Usually an 8 weight blank carries 5/8 oz tops, and it will be a sluggish.

Ok now i Know this information
(1)i would like to use a 8 Weight fly line
(2)i would use about 1 ounce probably not even that bacause i would float fish with it
(3)the weight of the fly line is 3/8oz
(4) still not sure
(5) i would like to use a 12ft rod but any thing over 9ft is ok
(6) would you find out the blank for me because i would not chose the right on as i have never made a spin fly before

I think that you are trying to get too much out of one rod. Build an 8wt fly rod and a spinning rod to the specs that you require.

Don