New Two Cylinder Engine, 2 Stroke or 4 Stroke? | Stirlingkit

hello guys. i need your help. our team is thinking making a new 2 cylinder engine. it's water-cooled. 12cc. independent valve.
but here are two problems.

1. we are not sure to make a 2 stroke or 4 stroke engine. which one is better? if it's a two-stroke, we will make it 28cc. if it is a 4 stroke, we will make it 12cc.

2. the gear timely belt is designed in the middle of the engine to make it more compact. but we are also worried if the belt can stand the high temperature or wear when the engine is starting up.

what do you think? any ideas are much more appreciated. thanks in advance. and welcome to send me an email service@stirlingkit.com

https://www.youtube.com/watch?v=Cz2mEyEHNQI