You can use a bias front tire with radials on the rear of a trike, most are used that way and have been for many years as there just weren't any radials for the front of a trike. The 130/70R18 Avon Cobra TRIKE Radial(# 90000020646) works well on front of a trike, it's what it was designed specifically for (so no reason to reverse it).
Back in the '60s when radials first started showing up on American highways the warning was always run in full sets. They handled different than the then available bias ply, often unbelted, skinny tires. Radials sidewalls bulged more, they would squirm a slight bit but had better steering response than bias ply tires, running radials on front with bias on rear made for real tricky oversteer. It was however, very much the opposite when bias ply tires were run on front and radials on rear, even on a car. Steering went more towards understeer, even plow as the rear of the car stayed planted. In time, the rule changed to yes, you can mix two radials with two bias ply tires as long as the radials are paired on the rear axle.
In 1965 Dad got a new Plymouth SW and soon he and some buddies at GE got a group order together and got a bunch of Michelin Radial X tires, they were great .... but people were always trying to tell us the tires were low. In 1972 a couple years after Dad passed away, my Mom and Sis and I went on a vacation trip to West Texas. Had our '68 SW checked over and alignment done. 1st lunch stop at Abingdon, Va. found front two tires near bald on edge ..... bad alignment. Went to local Ply dealer, they realigned it .... then local Sears for two tires .... put two 8.25x14 bias ply tires on front over objections of tire sales guy who was adamant we needed two more 215-14 Radials like on rear .... car drove GREAT, even at high speed on I-81 & I-40. Didn't buy two radials as rears were 1/2 worn anyway, she sold it the next year and bought a '73 Satelite Sebring Plus with Goodyear Polyglass GT rubber.