Can I temporarily use a BT30 (or iso30) toolholder in an R8 spindle? (with suitable draw bar)

I need to get a few quick jobs done with the mill (warco WM18) before I look to fully install an ATC. i need repeatable Z but I don't want to invest in any more R8 bits or parallel shank ER collects as I will probably go with a Bt 30 setup.

I know the tappers and the start diameter are the same and Im only using small 5mm cutters in Ali and side cutting Stainless.

Open to other options. cheers