The Pele Yoetz is very against shaving/trimming, saying that is will cause harm. However, I doubt it was meant to be L’Halacha (rather Kaballah — the Zohar is very intolerant). In Machne Yisroel, the Chofetz Chaim too is very Machmir. However, many Poskim permitted shaving as is stated in Tur (Hichos Rosh Hashana 582). Of course with a Hechsher.
It should be noted that there is a dispute on the Nusach HaTur (Mechaber skips it). Look in Ohr Zarua (2;257), Shut Rivash (513), Biur HaGr”a (582), Tashbeitz (1;157), Shut Minchas Elazar (2;48).