Lots of questions!

Some thoughts:
Yes, remote blower can be use with horizontal duct run. Could use an external blower mounted on the wall, or, if you had the room (i.e. the duct is running through an attic), an inline blower.

48'' BS range?? You need major cfm. I would get as much as the budget allows, at least 1200 cfm. I think 600 cfm would be way short of what you'd want when you're searing over 22,000 BTU's.

Modern Aire will sell to you direct if they don't have a local dealer. I just placed my order with them. They have been unbelievably helpful: ask for Jeff Herman if you need advice.

We have a VAH at the lake, and despite some of my reservations, it's still a good solid hood. For our main house though I clearly wanted major league cfm, with a remote blower and am going with the Modern Aire liner, and the Fantech FKD 10XL 1200 cfm inline blower and the Fantech silencer which will go into our attic. I love the flexibility of the Modern Aire (for the roughly $165 custom charge I have been able to specify the exact width, length, and location of the ductwork to the inch).

General rule of thumb is divide total BTU output by 100. For electric ranges, multiply total watts by 3.5 to get equivalent BTU.
Below is a link to a site with tons of calculations and information about this topic.

Here is a link that might be useful: CFM Requirements

We have a 48" Bluestar cooktop with a 24" grill. The duct run is 20Â with one 90 degree turn. Based on recommendations from Trevor at Eurostoves and Prestige technical support we went with a 58" Prestige liner with a 1600CFM external blower. A 1200CFM blower would have worked, but because I really like to use the grill and my design includes makeup air we decided to up the blower capacity. With a variable speed blower you can always back it down. It works great.

If you really intend to use the grill, a large, high capacity hood is a good investment.

clinregsa, i thought you were getting a hood from metallo arts?

Here is a link that might be useful: i thought you were getting this range hood?

No: actually I was castigated in another thread for failing to mention metallo arts. The issue was where to get a custom sized hood liner, if I recall correctly. I've just finally placed our order to Modern Aire for a 64'' wide hood liner that will go into our range alcove. To be coupled with a Fantech FKD 10XL remote blower and silencer to be placed in the attic. Good memory on your part, though (something I can no longer lay claim to).

Oruboris - I purchased a hood from Rangecraft. I can't say enough about its performance and fit & finish. I also had to have the ducting set offcenter in the back, which calculation changed during my remodel. The hood arrived to my specifications - the 2nd set. The really do beautiful work.

For serious ranges like the one you're planning, the hood should ideally be a bit wider than the range's width, and should be deep enough to cover the front burners half way.

Remote blowers are quieter, but air noise can still be a problem, which you can reduce by selecting a unit with a large surface at the air intake.

Whatever benchmark you use for determining the CFM capacity, make sure it takes into account the length of the duct and any turns, and remember turns have to be GRADUAL. With such high CFM capacity, you should plan on make up air. And you may want to heat the make up air if you're in frigid climate. If you're not sure you will need make up air, design things so that it can be put in later if needed.

Good luck.

Yes, the important thing to recognize (among many, I suppose) is that the fans are rated at zero static pressure loss, but in reality there are losses at the hood transition, the hood filtering system, along the ducting, particularly at bends, and at the fan transition. Then there is the loss due to depressurizing the house running the fan. Even with a make-up air system, the net house pressure will usually be a bit negative.

Hence, the actual cfm pulled through the ducting will be less than the rated performance of the fan, perhaps only 2/3 that of the fan rating. This means that after you decide what cfm you need, you need to upsize the fan somewhat to account for pressure loss.

kas