The 417A was designed as a grounded-grid UHF and low-microwave RF amplifier, the multiple grid connections were in order to reduce the inductance of the connections from grid to RF ground. As Gingertube says, the thing has scarey-crazy
transconductance, and it WILL oscillate at the slightest provocation
http://frank.pocnet.net/sheets/049/5/5842.pdfFor audio frequencies, I'd just connect all four grid pins(4, 5, 7 and 8) together, and use a single 1K ohm, carbon grid stopper resistor. Might not hurt to use a plate stopper (100 to 220 ohms) too, small enough so it won't adversely affect the circuit gain, but sufficient to reduce the probability of spurious RF oscillations, in conjunction with the tube's internal capacitances. Connect it between the plate, and the plate load resistor / coupling capacitor junction.
If you do choose to use five separate grid stoppers, make each one approximately four times the normal resistance for a single GS resistor (think parallel resistances) , otherwise their efficacy could be compromised.
Or just "cheap out" and use pins 4 and 7, that should be more than sufficient.
With its relatively low internal plate resistance of 1600-1700 ohms, and its 4.5W PD, the 417A / 5842 could be used in a single stage "spud" amp, with a 5K primary winding, with 750-900 mW power output.
/ed B