Personally, in most conventional aeroplanes, I have come to the conclusion that it is inappropriate to modify the approach speed for an approach in gusty conditions. If you work through the maths, approaching faster, only increases the gust response.
But, it is appropriate to approach with a bit less flap, so long as there's enough runway - which in strong winds, there generally is.
With less flap, stall speed goes up, and so should approach speed. Both go - at first approximation anyhow - with the square root of mass.
I can only think of one aeroplane I've flown with negative flaps, and it's not got an MTOW of 2400 lb (plus the training wheel is at the wrong end), so I'm not sure what type you're referring to. However, in general terms, flying a negative flap approach sounds like a bit overkill. However, let's look at the zero flap condition.
If VS1=55mph is the MTOW stall speed with zero flap, and you're approaching at 1860lb, then my first stab at an appropriate approach speed would be:
55 x 1.3 x SQRT(1860/2400) = 63mph.
Which intuitively feels about right.
I think you've got the right general idea, it's just a case of getting the numbers right.
One caution, at very high flap settings and low speeds ASIs tend to underread, if the approach speed is much more than 30% above the stall speed, factor the approach speed, not the stall speed - which may give you a dangerously low approach speed.
In a taildragger, I'd also in those sort of conditions seriously consider flying a wheeler landing rather than a 3-pointer as well.
G