If it survives ECM preparation, what polynomial would you use for 919^87-1? I'm thinking

x^6 + 919x^3 + 919^2, x=919^10

That results in SNFS size of 178, which is a little small for a sextic. But for a quintic I only see

x^5 + 919^7 * x^2 + 919 x=919^12

and that coefficient of 919^7 looks too large.

(Both derived by dividing out 919^29-1 and figuring an SNFS polynomial for

919^58 + 919^29 + 1

Is there something better I have missed?