A standard rule of thumb is that you're going to will need the turning issue on the crystal to get 10°C larger when compared to the higher running temperature in the OCXO oscillator circuit. The essential constructing block for any TCXO is a VCXO with somewhere around ±50 ppm deviation https://temperaturecompensatedcry04715.ivasdesign.com/52827168/not-known-facts-about-tcxo-oscillators