4th floor is 5th storey yes? If so G,1,2,3,4? 45ft may still be tight.
Might be a bit late now but i've been toying with the idea of getting one of those lazer tape measures. Point it to the top of the glass from where you'd stand and then there's no ambiguity as to the length you'd need.
Seem to be pricey but thought it'd look good when quoting to the customer though.