You may have to add some adjustable stops for the turning angle of the front forks ?
Why you ask .....
Well your tyres are not smooth and those lumps on them may seriously divert the chain from it's chosen path , this will most likely occur when manouvering the trike and trying to go backwards...
Hard and fixed ?
There are other ways gaining favour for the return idler ?
Or I bet this appeals to you ?
Or a simpler way is to just suspend it on a short length of brake inner cable , then it is free to go where it pleases ?
Don't forget a keeper for the power side idler ?
Yes with you on 3mm plywood and screws , it is likely they are very thin and only there as a clamp whilst the glue dries and the fillets are added , however screwing them in must be butt clenching !
I sold you a bit short with my post.
It is mentioned here :- Velomobile forum de
They have now added Iceland to the places you have a compulsory 14 day quarantine after you have been.
I only went for a bag of oven chips !
[ for non UK people an Iceland shop sells frozen food in the UK ]