Between sizes on Speedmax CF8?

Hi!

I’ve been cycling for just over two years now. Around 1,5 years ago I bought my first Canyon Endurace CF SLX 7 Di2 size M. I’ve been riding lots and lots of hours on it and been mostly really happy with it, though at times I’ve felt it to be a bit too small for me.

I‘m 184,3cm tall and (whatever the name for that is) the space between my legs is 87,8cm high, according to my bike fitting on the Endurace. Thing is that I am more on the heavy side with around 100kgs (started at 120, so there’s that) and the M sometimes feels a bit small for my frame. The bike fitter said that M is the correct size but I‘m hearing from so many people that my bike looks too small for me.

I plan on buying the Speedmax for an upcoming long distance triathlon in June and in general I’m planning on doing lots of triathlons in the future. Would it be wrong to just buy an L to be a bit more comfortable on that? Or is test riding both sizes needed? (I do live 2 hours away from Koblenz so I could go there for testing)

Really looking for some insights before committing to the purchase.

Thank you!