Can you/would you adjust timing to that for a higher category aircraft(I know in a normal situation it is not allowed)however the higher category aircraft will have a different /extended area of operation?
Of course you're going to time for the approach category in which you're operating. Whether you're another approach category or not is irrelevant: use the numbers appropriate to the speed at which you're flying. Use the higher minimums, and the appropriate times.
Where is using the next highest category minimums not allowed? All you're doing is being more conservative, and in this case it's a necessity, because you're flying the approach faster.
With this in mind, do you know your landing performance flaps-up, and given the limitations already imposed, do you still have adequate runway?