I have used Crisp Amber malt only a couple of times, and and only at 5%. Will be curious to hear responses from those who have.
This malt, like many others, seems to vary considerably by maltster. Below are descriptions of 3 maltsters from their or their distributors' websites. Note Simpsons max. usage is 20%. Am curious if Mosher mentioned a specific maltster?
Crisp- William Crisp Amber Malt is a kilned specialty malt. It has a strong biscuity, toasted grain flavor and imparts amber and copper hues. Amber malt is traditionally used in medium or dark English ales, especially brown ale, mild ale, and old ale. The dry taste of Amber malt is an excellent compliment to bitter hoppiness, making it a nice addition to IPAs. The color is listed at 23-35 L, and usage up to 10%.
Simpsons- Perhaps the most versatile of all our roasted products, Simpsons’ Amber Malt can be used in a wide variety of beers to add biscuity toasty notes and a beautiful brown hue. Its delicate roast flavour makes it suitable for adding toasty notes to all Dark Beers, as well as lighter Ales and Lagers. Amber Malt brings a clean, crisp dryness to balance delicate floral hops and increases foam stability. Color 54-71 EBC (21-27 L), and usage up to 20%.
Dingeman- The intensive germination and a mildly kilning will add a very strong malt aroma and a deep reddish color. Amber malt clearly improves flavor stability. The malt is rather low in diastatic power therefore it can only be used up to 30%. Color 19 L.