Hello Madboat.
Maybe I can share my own experience with you.
There is two Cristal engines : the 3,1 cc and the 4,5 cc.
They both are very good and powerful engine. The 3,1 cc fits perfectly the Topaz which wheight is less than 5 kg for a narrow 110 cm hull.
I must say that My Anton 6.7 cc Topaze engine drives a 13 mm 3x blades prop in a 27 kg tug. This , to say that Anton engine develops a good torque.
The Lancelot is given for 23 kg and 140 cm.
https://www.mountfleetmodels.co.uk/downloads/sirlancelot_mm_07-04.pdfI am afraid that the Cristal is a bit short for such a model.
I have build the Boston Typhoon whis is about the same size.
First of all I have thrown away almost all of the metal parts. They are heavy and a kind of coarse. That’s a lot of weight in the height too.
My boat weights 20 kg when I have added the dead weight in the boat hold to keep her in line.
But I had to install a +/- 9cc PM Research engine to be confortable. The propeller is a 3 blades / 70 mm cheap Rivabo but it deserves a better prop to add more power.
Below is the link where you can see more.
https://modelismenavalradioc.forumactif.com/t1200-boston-typhoon-de-kbio?highlight=boston+typhoonI hope its help. I'll be glad to follow your build !
Regards.
ps: for your information, ANTON does not supply boilers anymore.