Named Formula For Mega Nested If Statements

creating Named Formulas to handle nested IF & And statements, to get around excel's limit of 7 nested IF statements.

First of all, is it possible to create a Named Formula with combined IF with AND statement such as: =IF(AND(F26>=54,F26<=77.99),"2x3"," ")--I am getting a periodic error message: "Cell with block IF function should not contain anything else."?

I am trying to: 1. Contstruct two separate Mega formulas using IF & AND to determine what range of sizes , located in Col "F", should fall into which SIZE_CAT, sample of ranges are as follows:

SIZE_CATSIZE IN TOTAL INCHES
2X3 54 thru 77.99
3X5 78 thru 108
4X6 108 thru 138

2. Name these two formulas, FirstNamed and SecondNamed

FirstNamed formula is:=IF(AND(F26>=54,F26<=77.99),"2x3",IF(AND(F26>=78,F26<=108),"3x5",IF(AND($F26>=108,$F26<=138),"4x6",IF(AND($F26>=138.01,$F26<=168),"5x8",""))))
SecondNamed formula is:=IF(AND($F30>=168.01,$F30<=198),"6x9",IF(AND($F30>=198.01,$F30<=234),"8x10",IF(AND($F30>=234.01,$F30<=270),"9x12",IF(AND($F30>=270.01,$F30<=320),"10x14",IF(AND($F30>=320.01,$F30<=500),"Larger","")))))
3. Combine two named formulas with a "Master Formula" such as:
=IF(FirstNamed,FirstNamed,SecondNamed)

I got the IF with AND formulas to work in a test columns, but cannot seem to get them to respond properly when trying to get them into a Named Formula(s).

I have attached an example of the workbook.