iCE40 Ultra Plus 5k -- how to set PLL (without propietary GUI tools)

Is there any way to configure the iCE40 Ultra Plus 5k PLL without using the fancy propietary tools like Lattice Icecube2 / Radiant software.

Official PLL programming guide (source) only shows how to use mentioned propietary GUI tools (ch. 4)

Those tools simple generate the files needed. In the end it looks like this:

module main_pll(REFERENCECLK,
            PLLOUTCORE,
            PLLOUTGLOBAL,
            RESET);

input REFERENCECLK;
input RESET;    /* To initialize the simulation properly, the RESET signal (Active Low) must be asserted at the beginning of the simulation */ 
output PLLOUTCORE;
output PLLOUTGLOBAL;

SB_PLL40_CORE main_pll_inst(.REFERENCECLK(REFERENCECLK),
                            .PLLOUTCORE(PLLOUTCORE),
                            .PLLOUTGLOBAL(PLLOUTGLOBAL),
                            .EXTFEEDBACK(),
                            .DYNAMICDELAY(),
                            .RESETB(RESET),
                            .BYPASS(1'b0),
                            .LATCHINPUTVALUE(),
                            .LOCK(),
                            .SDI(),
                            .SDO(),
                            .SCLK());

//\\ Fin=13.56, Fout=40.68;
defparam main_pll_inst.DIVR = 4'b0000;
defparam main_pll_inst.DIVF = 7'b0101111;
defparam main_pll_inst.DIVQ = 3'b100;
defparam main_pll_inst.FILTER_RANGE = 3'b001;
defparam main_pll_inst.FEEDBACK_PATH = "SIMPLE";
defparam main_pll_inst.DELAY_ADJUSTMENT_MODE_FEEDBACK = "FIXED";
defparam main_pll_inst.FDA_FEEDBACK = 4'b0000;
defparam main_pll_inst.DELAY_ADJUSTMENT_MODE_RELATIVE = "FIXED";
defparam main_pll_inst.FDA_RELATIVE = 4'b0000;
defparam main_pll_inst.SHIFTREG_DIV_MODE = 2'b00;
defparam main_pll_inst.PLLOUT_SELECT = "GENCLK";
defparam main_pll_inst.ENABLE_ICEGATE = 1'b0;

endmodule

However, the use of the tools is recommended to correctly set all the parameters. Any reason against using the freely available tools to generate the files and then use it elsewise?