Cutting Back Sugar?

I don't think that It matters all that much. I know that you cream the butter and sugar to help leven the dish, I think that if you got rid of the sugar all together then you may have problems, but cutting it down a little should not hurt.

KYH, since I'm living in a country where most people eat potatoes every day, I am interested in this kind of stuff. I never heard of a potato dish in which sugar was involved, which doesn't mean it does not exist, I would dare make a guess it's scandinavian, but the rose water, that's arabic and they don't eat potatoes. To be frank, sugar and potatoes are a big no for me.

I'm also thinking of the potatoblinis I make with gravad lax. In fact they are small pancakes but without the sugar. Basically it's potato, 20% of that volume flour, an egg, a dash of cream and add milk until you reach a stage where the dough has the consistency of mayo, seasoning. Fried in a pan, they go fluffy and very tasteful even without sugar.

When I read your ingredients and the quantities you use, I'm very sceptical about the measurements. If it were me, I would make these changes;

1 lb potato
¾ lb butter; 250 gram (1/2lb)
½ lb sugar; I would leave that out completely and go for salt and pepper. Maybe some flour instead?

¾ cup milk or cream; I would go to 750 ml since you're using a very big quantity of eggs. This quantity of milk will match the eggquantity. Of course, the eggs will make the dough raise while baking and come down again when cooling.
Juice and zest of one lemon
2 tsp nutmeg; that's an enormous amount, I would go for just a pinch
4 whole eggs
3 egg yolks
2 tsp rose water; that's absolutely too much, a few drops will already be more than enough, that stuff is much too overpowering. 

This looks like it's a variation on an old dish from the south-west of the UK. This wouldn't originally have contained rosewater and would probably use something like brandy instead. The original reason for the use of potatoes as starch is simply that they're the main arable crop down there due to the nature of the soil.

I wasn't really trying to suggest that you change it, just hoping to shed a bit of light on its origins. There was fairly heavy migration to North America from the UK around the time the potato was gaining in widespread popularity as a foodstuff (1740s & 1750s) and the recipe probably came across sometime then. Virginia in particular had a lot of migrants from Cornwall, where the old dish I mentioned originates - it's an almost identical dish. Does the cookbook have any more information on this, I wonder?

It should be safe to cut down the sugar by about a quarter without causing many problems, if the texture changes markedly you could try removing the white of one egg to compensate.

KYH: 

Never heard of it but it sounds good. I am going to make a small batch I am going to add a touch of cinnamon.

     I normall make a savory potato pudding or kugel type cut in triangles to be served with the roast.

I can tell that by looking at formula. And as I said mine is savory.  You could also use noodles , like a sweet noodle pudding.

I use the same formula for Kugel that I do for potato latkas only a little more egg, so it stays moist . I now make it in cupcake pans, so I dont have to figure portions. I figure 2 cupcakes  pp.