Trying to modify a recipe

I pulled a recipe from a book and here is what I ended up with. I currently have this batch in the secondary as follows:
5lb Amber DME
1/2 lb 20L Crystal malt
1 1/2 oz Cascade (5.3%) 60 min
1/2 oz Willamette (4.1%) 5 min
2 tsp. gypsum
nottingham dry ale yeast

I tasted this as I took a hydrometer reading to see if it was finished in the secondary and liked it. As this is only my second attempt at brewing I would like to do the same thing, except I want to alter the malt profile using a partial mash. I want to be able to taste the differences of using a partial mash vs. total extract without changing the hop profile so much. My question is how much DME and grain do I need in this new recipe? I was tinkering around with Tastybrew.com and came up with something like this. Any advice is GREATLY appreciated.

2 lbs Light DME
6 lbs American Two-Row Pale (mashed)
.5 lb 40L Crystal (steeped)
1oz cascade 60 min
.5oz cascade 30 min
.5 oz willamette 5 min
wyeast (which one!?)

Looking for a smooth American Pale ale that is very drinkable and to make all the friends jealous. Thanks

-Joe

I plugged your recipe into Promash and here are the results.

Joe's Amber Ale

A ProMash Recipe Report

BJCP Style and Style Guidelines
-------------------------------

10-A American Ale, American Pale Ale

Min OG: 1.045 Max OG: 1.060
Min IBU: 30 Max IBU: 54
Min Clr: 5 Max Clr: 14 Color in SRM, Lovibond

Recipe Specifics
----------------

Batch Size (Gal): 5.00 Wort Size (Gal): 5.00
Total Grain (Lbs): 8.50
Anticipated OG: 1.051 Plato: 12.63
Anticipated SRM: 6.9
Anticipated IBU: 35.7
Brewhouse Efficiency: 70 %
Wort Boil Time: 60 Minutes

Pre-Boil Amounts
----------------

Evaporation Rate: 22.00 Percent Per Hour
Pre-Boil Wort Size: 6.41 Gal
Pre-Boil Gravity: 1.040 SG 9.94 Plato

Formulas Used
-------------

Brewhouse Efficiency and Predicted Gravity based on Method #1, Potential Used.
Final Gravity Calculation Based on Points.
Hard Value of Sucrose applied. Value for recipe: 46.2100 ppppg
Yield Type used in Gravity Prediction: Fine Grind Dry Basis.

Color Formula Used: Morey
Hop IBU Formula Used: Tinseth
Tinseth Concentration Factor: 1.30


Grain/Extract/Sugar

% Amount Name Origin Potential SRM
-----------------------------------------------------------------------------
70.6 6.00 lbs. Pale Malt(2-row) America 1.036 2
23.5 2.00 lbs. Generic DME - Light Generic 1.046 8
5.9 0.50 lbs. Crystal 40L America 1.034 40

Potential represented as SG per pound per gallon.


Hops

Amount Name Form Alpha IBU Boil Time
-----------------------------------------------------------------------------
1.00 oz. Cascade Whole 5.30 20.2 60 min.
0.50 oz. Cascade Whole 5.30 7.8 30 min.
0.50 oz. Willamette Whole 4.10 7.8 60 min.


Yeast
-----

You can mash the Crystal right along with the 2 row. How are you going to mash the grains? This result is based on 70% efficiency of your mashed grain, so you might want to have some extra DME on hand if you want a higher Original Gravity. I would think that Wyeast 1056 - California Ale yeast would be a nice choice for the brew.

Thanks for the info. I think I made a mistake though. I didn't realize I was going to need to boil so much with those ingredients. I'm going to try to lower the amount of grain so that I can still use my 3 1/2 gallon brewpot. If all goes well I might invest in a larger pot.

I adjusted the grain profile to be:
4lbs light DME
3lbs 2row pale
.5 lb crystal 40L

That would mean a boil of just over 3 gallons in the brew pot correct?

As for the mashing I was looking at infusion mashing (?) maybe this should be moved to the beginner forum, but here's the plan:
heat water (5.5 quarts) to 150-158F and add crushed grain
check pH 5.0-5.5
hold at 150-158F for 60 minutes
raise to 160-170 for 10 minutes
strain into bucket
strain back over grains into brewpot along with sparge water (7 quarts)
now I should have approx. 3 gallons

You say I can add the crystal malt directly in with the mash? Sounds good/easier to me. Thanks.

I don't think that you would get 70% efficiency with that method although I'm sure that someone may have in their process. There is a great thread here on partial mashing and for a minimal investment I think your process would definately benefit. Here is the link > https://www.homebrewtalk.com/showthread.php?t=8805
Take a few minutes and try to read it as there is a lot to be learned and if you are going to be brewing for a while then I would think you may be happier with your brews. When mashing keep your temp stable as possible. I would recommend around 150-152 to get more fermentables out of the grain. I fall that you can boil is 3 gallons or so you might consider boiling for the most part with your mashing wort and adding the DME at the last 15-20 minutes of the boil. Keep the fermenting temps stable at 70 or a bit lower and your beer will benefit.