Thanks sabayonino and all who wrote the HOWTO's I consulted.
From a "little hen" so use with caution.
equo install eix # required below
emerge --sync # I think that this was sync was repeated with eix-update ?
layman -d sabayon
layman -l # to check that Sabayon overlay present
layman -a sabayon
emerge -av =tellico-2.3.4 # 2.3.5 is available, played safe. Only cmake and trellico pulled in so "Yes"
A quick test and Tellico is working as advertised.