Thomann Adapter French Horn - Trumpet

It's not the first time i tried this kind of adapter. The same problem happened. I pushed the french horn mouthpiece far behind from leadpipe. Must remember a french horn mouthpiece is extremely deep, pushing trumpet to a lower tunning in general, specially on high register. The main problem results in a very low tunning below A 440kHz, even when tunning adjustments set to the highest.
I can't use it when try to play with other instruments. So I'm using the french horn mouthpiece attached directly to the leadpipe and holding it with silver tape. In this way, it works correctly.