Hi Tom. It's actually far easier than you think. For one, the RM Italy 305V won't fry, it'll just cut at 10W in. If you give it 11 W, it cuts, period. I'd love to show you how I have it wired up in my car, it's sweet. I have two buttons labeled QRP and QRO. The QRP just PTTs the TXC. When the amp does not receive a PTT, it just lets the signal bypass, so I can tx up to 100W without the amp. If I want to go QRO, I reduce my TXC power to 10W and hit my QRO button which activates both my TXC and my RM Italy... sweet. I'm actually going to transmit my first car signal this Saturday at 8:30 AM from Gaithersburg. I'll be getting on 80M to join the Cherry Tree Net (regional net on 3920).
If you'd like to see my setup, glad to meet up (social distancing, of course). Otherwise, I can take some photos and show you. As for shots of Alan and James' rigs, I think we have some on the site somewhere. I'm going to look for them. I'll also ask @W4DOI and @W3JRD to post some of their own, if they have any. In their case, they drive the amp with a 7300. I used to, but I sold it. Like I said above, I'm thinking of testing out the Icom 705 when it finally arrives.
Here you go. Alan's is the first setup, and James is shots two and three.