Converting my meter development numbers to gear inches, I get 1.06m=13" and 1.30m=16". I find 16" still usable when you actually need it, and 13" just for short periods, when 16" is not enough. As to the 7.5" above, I reckon that hill could be ridden straight up on a higher gear without getting out of the saddle. You can use 7.5" at the cost of maintaining a rather high cadence. At the point where you would actually need to resort to 7.5", because higher gears were not enough, I claim you would not be able to use it and need to retreat to walking. On the side, the general problem with extremely low gears is that is very hard to shift between them when you are ridding uphill at a highly tensioned chain. With this,sometimes you may end up shifting preventively to the very low gear before the slope gets steep and continue for a while at an unreasonably high cadence.