Requiem Raspberry ale - Late DME addition help

I want to brew eschatz's Requiem Raspberry ale that is listed in the recipe section on HBT, but want to do Late DME Addition.
Here is the original recipe:
Recipe Type: Extract
Yeast: Nottingham Ale Yeast
Yeast Starter: none
Batch Size (Gallons): 5
Original Gravity: 1.054
Final Gravity: 1.014
IBU: 22
Boiling Time (Minutes): 60
Color: 13.9
Primary Fermentation (# of Days & Temp): 7 days at 73 F
Secondary Fermentation (# of Days & Temp): 7 days at 73 F

6 lbs 8.0 oz Light Dry Extract (8.0 SRM) Dry Extract 87.25 %
12.8 oz Caramel/Crystal Malt - 40L (40.0 SRM) Grain 10.74 %
2.4 oz Roasted Barley (300.0 SRM) Grain 2.01 %
1.00 oz Northern Brewer [6.60 %] (60 min) Hops 15.0 IBU
0.50 oz Cascade [6.40 %] (25 min) Hops 5.1 IBU
0.50 oz Cascade [6.40 %] (7 min) Hops 2.0 IBU
40.00 oz Raspberry Fruit (Secondary 5.0 days) Misc

Nottingham
OG 1.054
FG 1.012
IBU/SG ratio is .38

In Beersmith, I came up with the following:

BeerSmith Recipe Printout - http://www.beersmith.com
Recipe: Raspberry
Brewer: Brian Moore
Asst Brewer:
Style: Fruit Beer
TYPE: Extract
Taste: (35.0)

Recipe Specifications
--------------------------
Batch Size: 5.00 gal
Boil Size: 2.98 gal
Estimated OG: 1.058 SG
Estimated Color: 13.9 SRM
Estimated IBU: 19.2 IBU
Brewhouse Efficiency: - %
Boil Time: 60 Minutes

Ingredients:
------------
Amount Item Type % or IBU
2 lbs 8.0 oz Fruit - Raspberry (0.0 SRM) Adjunct 25.13 %
5 lbs 8.0 oz Light Dry Extract (8.0 SRM) Dry Extract 55.28 %
1 lbs Light Dry Extract (8.0 SRM) Dry Extract 10.05 %
12.8 oz Caramel/Crystal Malt - 40L (40.0 SRM) Grain 8.04 %
2.4 oz Roasted Barley (300.0 SRM) Grain 1.51 %
0.25 oz Northern Brewer [6.60 %] (60 min) Hops 3.7 IBU
0.50 oz Cascade [6.40 %] (25 min) Hops 5.0 IBU
0.50 oz Cascade [6.40 %] (7 min) Hops 1.9 IBU
1 Pkgs Nottingham (Danstar #-) Yeast-Ale


Mash Schedule: None
Total Grain Weight: 0.95 lb
----------------------------
Steep grains as desired (30-60 minutes)


All I am doing is starting with 1lb of DME and adding 5.5 lbs @ 15 min. To adjust Hop schedule I just changed Northen Brewer from 1oz to .25 oz to get a IBU of 19.2.

Is this change ok as far as the changes I made? It sounds like a great recipe and I want to keep it as close as possible to the original. Did I reduce the amount too much or should I use a different Hop with less AA% instead. If I should use a different one, can someone suggest a hop with similar characteristics, just lower AA%?

Or is someone has a Partial Mash for this one, I would like to try that as well
I appreciate the help, This site rocks!
Thanks for the help,
Brian

I see your boil size is just short of 3 gals.

Your steeped grains equal almost 1 lb. Steeping should give you about 40% efficiency. If you adjust your malt to a ratio of 1:1 with the water...3 lbs to 3 gals you won't have to adjust your hops at all.

I've made lots of batches this way. I start off with a couple gals of PUR filtered tap water placed in the freezer for 4-5 hours before using them as top off water.

I would add 2.5 lbs of DME to your steep water and go from there. Boil 45 mins, remove the pot from the heat and stir in the DME (1 lb at a time and dissolve then add the next pound, etc.) then let steep for the remaining 15 mins. Strain hops from wort and top primary off to 5.5 gals. Take temp and hydrometer readings. Chilled water should bring temps down to the 70s. Pitch yeast. Done.