For how long does the transfer press?
305 is not too bad, at least compared to the 375-390 or so that digital transfers require.
I regularly press name drop vinyl at 300 for 10-15 seconds without ruining the existing plastisol print.
I do dodge it when I can, and you were smart to take advantage of the clearance for it on this one,
but in a pinch, the two media can often play together with minimal segregation.